# MemScan

ROSE SWE, Ralph Roth

MemScan - Memory Scanner: A rule based, universal memory virus scanner for DOS viruses. Not limited to known viruses! Will not run on 64 bit Windows systems.

| Nowadays, pure DOS or Windows 9x and Win32 is hardly ever used, the main use case for which MemScan was developed. Nevertheless, we continue to offer MemScan for free use, because we believe that this is the only program that is still maintained and developed worldwide for DOS compatible operating systems!

         __  __                ____                     ______   ___  ____
        |  \/  | ___ _ __ ___ / ___|  ___ __ _ _ __    / /  _ \ / _ \/ ___|
        | |\/| |/ _ \ '_ ` _ \\___ \ / __/ _` | '_ \  / /| | | | | | \___ \
        | |  | |  __/ | | | | |___) | (_| (_| | | | |/ / | |_| | |_| |___) |
        |_|  |_|\___|_| |_| |_|____/ \___\__,_|_| |_/_/  |____/ \___/|____/

                                     (c) 16.10.1990-2025 by ROSE SWE, Ralph Roth

        $Id: MemScan_Eng.txt,v 1.50 2024/12/11 09:55:35 ralph Exp $
        Written in ASCIIDOC using the UTF-8 code set and Windows LF/CR
        Umlaute and screen copy may look ugly if our text program don't use UTF-8

| A short English "FAQ" for QMS, MemScan and TestBoot can be found at the end of the document!

## 1. Function of MemScan

MemScan examines your working memory for resident MS-DOS computer viruses. If you have further questions about computer viruses, please read the files VIRSCAN.DOC & VIRSCAN.TXT (if available).

MemScan can also check the "UPPER" DOS Memory (UMB = memory between 640 KB and 1 MB) and the HMA (High Memory Area = 1088 KB) gate. MemScan needs approx. 450 KB of free working DOS memory for the virus database and hash tables! MemScan main memory usage was adapted especially to network environments and therefore needs only 450 KB of free memory!

MemScan detects due to heuristic scanning unknown viruses (option /UNB). MemScan usually reports such viruses with one of the following messages:

    Execution-Function [Exec] or
    Generic File Open [Fopen] or
    Memory Control Of Blocks [MCB] or
    Generic Exeheader.????-???? or
    Generic Boot virus [BOOT] etc.

In case of detection of one of these two viruses please send me an infected file: To classify the virus (if VirScan reports the same virus type with the option /HEUR) and to include it in MemScan! Try to make the virus infect the "victim/bait/goat files" INFECTME.* included in this package!

| MS-DOS 6.xx and Novell DOS 7.0 produce a false alarm with the option /UNB together with the option /HIGH. In most cases a Generic Exec Virus is reported in the segment Fxxx:xxxx which, however, is occupied by COMMAND.COM loaded high.

## 2. Why MemScan?

We are using MemScan internally to quickly and securely add new viruses to VirScan. However, customers frequently asked us for a program that checks ONLY the working memory. For this reason MemScan was made accessible to the public for FREE.

## 3. Optional parameters

    /?                Displays a short help
    /HIGH             Search high memory (to 1 MB) too
    /IVT              Check interrupts for viruses, see also VIRSCAN.DOC
    /NOLIVEBAIT       Skip Live Bait Test
    /NOMEM            Skip complete "Quick Memory Check"
    /NOPATHCOMPANION  Skip path Companion Test
    /UNB /UNK         Search for new unknown viruses
                      No output on argument syntax (Guru option).
    /AKTION           Display information on virus special offer.

| To see a short description of more options execute MemScan with the parameter /? for a short help!

### 3.1. Option /UNB

This option is only for the case of emergency! This function ALWAYS produces false alarms! I use it for finding known and new viruses! Almost every new resident MS-DOS virus can be found with MemScan!

### 3.2. Option /IVT

With the parameter /IVT the working memory can be examined for approx. 180 of the most known DOS viruses. This is being done by so called "Am I there" calls in a split of a second (in comparison to the slow memory scan). Among other things, the working memory is being examined for the following viruses:

- Jerusalem and related viruses (at least 48 variants)

  - Frere Jacques

  - Fu Manchu

- Tequila (Stealth virus)

- Yankee Doodle/Vacsina (45 variants)

- Cascade and Yap (14 variants)

- Flip/Omicron (6 variant/Sub-stealth virus)

- Parity (4 variants, boot virus)

- dBase

- Plastique (AntiCad, Invader, Tobacco, 4.21, 5.21 and Cobol)

- Tremor (Stealth virus)

- Hare (Stealth multipartite virus)

On detection of the virus the user is being informed about that.

| You should not use this option if you have Novell Netware installed because it results in overlapping of the interrupt calls. This function used to be executed automatically, but it emerged that the so called "Am I There" calls were not 100% compatible with different operating systems and configurations. So, if unusual side effects occur, this option might be the reason. This option also checks the high memory (HMA) - if available - for viruses.

### 3.3. Notes on parameter usage

Customers familiar with the American or UNIX parameter syntax (minus sign) instead of the slash (/) can also use the minus sign (-) to start an option.

    Example: -IVT is equivalent to /IVT

| There must be at least one blank between the individual arguments! The arguments are not case sensitive.

### 3.4. The environment variable MemScan

Instead of always calling MemScan with arguments, MemScan can be controlled with a so called environment variable. For example, enter the following at the DOS prompt:

    SET MEMSCAN=/unb -high -IVT

If you start MemScan now, MemScan reads all required arguments from the variable.

### 3.5. Rollback of preset values

Sometimes it might be desired to reset already set options (i.e. set by SET MEMSCAN=…) This can simply be done by a minus sign following the option on the command line. With this action the option is being switched off.

For example, you have entered the following:

    SET MEMSCAN=/high

Then start MemScan with the following argument:

    MEMSCAN /high-

In this case the command line option overrides the option set by the environment variable! Command line always override environment options.

## 4. False alarms of MemScan

MemScan detects approx. 98% of ALL new resident DOS or boot viruses with the option /UNB; however, this option is only for absolute virus gurus. Hint: If you suspect a virus on your system, execute VirScan Plus with the following parameters:

    Virscan -auto -HEUR -log

| If VirScan Plus finds in several EXE/COM files the same virus as MemScan: New virus! If VirScan finds a different virus in many COM/EXE files, for example: Crypt/FamZ, then it is a new ENCRYPTED virus! In these cases please send me an email with the infected files! Note: The option /HEUR is available only in the full version of VirScan Plus!

This screen shot is normally a false positive, because the "virus" is only found with

1. the -unb option

2. only in the main screen

    ¦¦¦¦¦+-----------------------------------------------------------------+¦¦¦¦¦
    ¦¦¦¦¦¦   MemScan 20.x.x - (c) 03.01.1991-2025 by ROSE SWE, Ralph Roth  ¦¦¦¦¦¦
    ¦¦¦¦¦+-----------------------------------------------------------------+¦¦¦¦¦
    ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦
    ¦¦+-------------------------------- Messages ----------------------------+¦¦¦
    ¦¦¦                                                                      ¦¦¦¦
    ¦¦¦  ¦ Free memory available for MemScan: 68.000/68.000                  ¦¦¦¦
    ¦¦¦  ¦ Command line: -unb                                                ¦¦¦¦
    ¦¦¦  ¦ Signatures created: Mi 25. Feb. 2004, build 3.073, 5.165 signs    ¦¦¦¦
    ¦¦¦  ¦ This PC has 640/640 kb free base memory                           ¦¦¦¦
    ¦¦¦  ¦ HMA/A20 gate present at segment: 0xFFFF:0000                      ¦¦¦¦
    ¦¦¦  ¦ Checking conventional memory (640 kb)                             ¦¦¦¦
    ¦¦¦  - Found the Type_Exec2a.35C6-D0A0 virus!                            ¦¦¦¦
    ¦¦¦                                                                      ¦¦¦¦
    ¦¦¦  Warning: A virus found in your main memory!                         ¦¦¦¦
    ¦¦¦                                                                      ¦¦¦¦
    ¦¦¦                                                                      ¦¦¦¦
    ¦¦¦                                                                      ¦¦¦¦
    ¦¦¦                                                                      ¦¦¦¦
    ¦¦+----------------------------------------------------------------------+¦¦¦
    ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦
    ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦+---------- Scanning ---------+¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦
    ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦     Please press a key!     ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦
    ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦+-----------------------------+¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦
    ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦

A normal virus infection looks like this, and MemScan won’t go to the main screen at all (in this case a 572 byte long new DOS COM infector):

    -----[ Quick scan of the system and memory for viruses ]----------------------

      MBR - HDD 0 (512) .......(45FC:2A00)..... -- OK! --
      Interrupt 13h (DOS) .....(0D58:18C5)..... -- OK! --
      Interrupt 13h (Orig) ....(F000:E3FE)..... -- OK! --
      Interrupt 21h (DOS) .....(9F75:0119)..... Type_Exec1a.4A77-F232 Virus
      Interrupt 40h (DOS) .....(F000:EC59)..... -- OK! --
      Memory (Low-System) .....(0000:0000)..... -- OK! --
      Memory (639 KB) .........(9C00:0000)..... Type_Exec1a.4A77-F232 Virus
      Memory (HMA) ............(FFFF:0001)..... -- OK! --
      HDD-IRQ 76h .............(0CC5:0117)..... -- OK! --
      Path Companion Test ..................... -- OK! --
      Live Bait Test ..........(295 KB)........ Type: COM=572 Virus
    Heuristic mode:
      Single Step .............(0070:06F4)..... -- OK! --
      Misc BIOS ...............(0D58:19A0)..... -- OK! --
      Reboot ..................(0D3B:002F*).... -- OK! --
      Multiplex ...............(14E2:1180)..... Type_Exec2b.CF14-B4E4 Virus
      VCPI ....................(F000:FF53)..... -- OK! --
      Interrupt D3h ...........(F000:FF53)..... -- OK! --
      Interrupt 0Dh ...........(F000:FF53)..... -- OK! --
      Interrupt 0Eh ...........(0CC5:00B7)..... -- OK! --

    Please deactivate the virus through a cold boot from a system disc!
    Press any key to continue...

## 5. Program Return Values

MemScan return an error-code back to DOS that can be evaluated by the variable ERRORLEVEL. The following error-codes are used:

            ERRORLEVEL              Short description
            -----------------------------------------------------------------
            0                       All OK, Option -?, -h etc.
            1                       Internal error
            2                       Option -exit
            3                       Overlay (MemScan.ovr) handling error
            8                       Not enough free memory available

            10                      QuickMemoryScan found a virus
            11                      NOSTEALTHTEST found a virus
            12                      NOWINTEST found a virus
            13                      Found a virus in the main scan function

## 6. Hints and FAQ

Q: can you help me fix the virus on my main memory…? attached is the view of MemScan and QMS…

A: I think this is a so called "false positive". Please read the attached document (MemScan_Eng.txt). If you have a DOS or boot virus, you should be able to trace it (as described in MemScan_Eng.txt) with QMS/MemScan and VirScan Plus. What DOS Version and Windows Version do you use. Some special DOS drivers in usage?

Q: Only the TESTBOOT routine found something. Since it was in German, I really didn’t know what it said. I went to an online translator and realized that it said "wert ermittelt" and "wurden gesichert" which translated "worth determines" and "became secured". After that I ran it again and it didn’t

A: That’s normal for the first (initial run) - I have added were possible an English translation in the new version!

| How you can possibly detect a file-/boot virus:

1. MemScan -unb -high

2. QMS -unb

3. put testboot.exe into the Autoexec.bat as last command (DOS/Win9x based systems only)

4. rhbvs -auto -log -all -high

## 7. Integrated virus protection

The program contains an integrated check-sum tester to alert the user on a possible virus infection. The check-sum for the program can be found in the file with the extension ".XXX".

This check-sum contained in the file as well as the main program must not be changed nor modified in any case! Otherwise, the main program regards itself being possibly infected by a virus (a virus still unknown to the program)!

Following features of the EXE file are monitored and checked for modifications every time the program is executed:

- Check-sum (CRC32) - If only one bit of the program is changed by a virus, the

- check-sum will no longer match (own secure routine, according to ANSI X3.66 -

- CRC-Poly is: 0xDEBB20E3).

- File size - If a program becomes one or two KB longer, it is infected!

- Overlay size - If the program uses overlays (".OVR").

I strongly recommend not making any changes to the EXE & XXX-file since the program will not run any more!

The file with the extension ".XXX" also contains the creation date and the standard MD5 checksum that can be checked with other tools like md5dir or hashall from ROSE SWE. Verifying the CRC32 checksum takes less than 1 second (depending on computer type and hard disk drive). If the check-sum is OK, the program is being executed. Otherwise a detailed error report with indications of possible error reasons will be displayed.

This is a screen shot of MemScan self check envelope finding itself infected with an 647 bytes EXE infector!

    #####   Länge der Datei MEMSCAN.EXE hat sich geändert!   #####

    Hierfür gibt es mehrere Möglichkeiten für diese Fehlermeldung:

    ¦    Ein Virus hat das Programm befallen!
         Am besten gleich mit VirScan Plus testen ...
         WARNUNG: Programm ist um 647 Bytes größer geworden!!!
         SENDEN SIE UNS DIESE DATEI ZU ANALYSEZWECKEN ZU! TYPISCH FÜR VIREN!

    ¦    Sie haben die Datei MEMSCAN manipuliert, deshalb ist die
         Checksumme verändert worden.

    ¦    Sie haben nicht alle Dateien mit kopiert (s. o.), oder auf dem
         Datenträger sind Informationen verloren gegangen (Bits umgekippt).

    ¦    Verwenden Sie die Option /NOCHECKCRC um diese Überprüfung zu umgehen!

    Bitte die ENTER-Taste zum Fortsetzen drücken...

## 8. Other/Misc

If you want to obtain the full versions of my antivirus software, please start the program REGISTER.COM, and an order form will be printed.

By the way: MemScan is compressed from 380 KB to currently 87 KB EXE + 183 KB overlay!

## 9. Reviews/Awards

https://www.windows11downloads.com/win11-memscan/ (MemScan 23.5)

## 10. What’s new?

    Version             Changes
    #######################################################################

        3.00            Parts of MemScan were swapped out to the overlay
                        file MEMSCAN.OVR, therefore MEMSCAN needs 50 KB less
                        working memory. Added checksum tester.
        3.10            Extended 'Am I There' Virus test.
        3.17            Program does not wait any more for key stroke
                        if NO virus was found!
        3.33            Number of detected viruses: approx. 3.000!
        3.36            The package now includes HMS.COM.
        3.50            Live Bait Test to detect
                        unknown file viruses.
        3.53            New ChkPC version (Hare & Boot-437)
        3.55            50 new viruses, i. e. CriCri & Grief.
        3.98            4180 viruses. QMS, TestBoot & HMS were
                        considerably enhanced. The Live Bait
                        Test was considerably enhanced.

        4.xx            New Viruses.

        5.0.1           Completely redesigned version. Program in English!
        5.1.0           Added Stealth Live Goat Test.
        5.6             /NOPATHCOMPANION, /NOLIVEBAIT
        5.7             /NoMem
        6.0             Win32 Live Bait Test
        6.2.7           /NoWin32Test, /NoStealthTest, DOKU revised
        6.3.1           This English documentation added
        6.5.5           /NoHMA fixes, A20-Gate/HMA fixes
        6.6.8           Tons of new viruses due to F_Mirc Linux porting
        9.5.5           adapted to run with DosEMU (Linux)
        9.5.8           30.08.2017 - Ported this documentation to ASCIIDOC
        10.1.5          22.01.2018 - new viruses
        23.5            April 2023 - new viruses
        30.0            June 2024 - new viruses, maintenance release

## 11. BANNERWARE from ROSE SWE

This program may be freely copied and passed on. It is considered as so- called Bannerware. I only request the following declarations to be kept:

- ©opyright by ROSE SWE, Ralph Roth (the so-called Banner)

- sale and/or industrial transmitting of the programs is forbidden. No commercial transmitting without ours hard-copy consent!

- the programs MUST distributed free and/or passed on against a small copying-charge (Shareware trader) (max. EUR 10,--).

- the program/documentation must not be changed!

- the program package must be passed on complete and unchanged!

Trademarks of other companies mentioned in this documentation and package appear for identification purposes only and are property of their respective companies.

NOTICE TO USER: You should read the following terms and conditions carefully before using this software. Your use of this software indicates your full acceptance of this license agreement and warranty. BY INSTALLING THIS SOFTWARE YOU ACCEPT ALL THE TERMS AND CONDITIONS OF THIS AGREEMENT.

The SOFTWARE is owned and copyrighted by ROSE SWE. Your license confers no title or ownership in the SOFTWARE and should not be construed as a sale of any right in the SOFTWARE.

No Warranty. The Software is being delivered to you AS IS and ROSE SWE makes no warranty as to its use or performance. ROSE SWE AND ITS SUPPLIERS DO NOT AND CANNOT WARRANT THE PERFORMANCE OR RESULTS YOU MAY OBTAIN BY USING THE SOFTWARE OR DOCUMENTATION. ROSE SWE AND ITS SUPPLIERS MAKE NO WARRANTIES, EXPRESS OR IMPLIED, AS TO NON INFRINGEMENT OF THIRD PARTY RIGHTS, MERCHANTABILITY, OR FITNESS FOR ANY PARTICULAR PURPOSE. IN NO EVENT WILL ROSE SWE OR ITS SUPPLIERS BE LIABLE TO YOU FOR ANY CONSEQUENTIAL, INCIDENTAL OR SPECIAL DAMAGES, INCLUDING ANY LOST PROFITS OR LOST SAVINGS, EVEN IF AN ROSE SWE REPRESENTATIVE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES, OR FOR ANY CLAIM BY ANY THIRD PARTY.

In short: This software is provided as-is, without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software. If you do NOT agree simply do NOT install and use this software!

## 12. Copyright

    (C)opyright by (ALL RIGHTS RESERVED!)

    __________ ________    ____________________   ___________      _____________
    \______   \\_____  \  /   _____/\_   _____/  /   _____/  \    /  \_   _____/
     |       _/ /   |   \ \_____  \  |    __)_   \_____  \\   \/\/   /|    __)_
     |    |   \/    |    \/        \ |        \  /        \\        / |        \
     |____|_  /\_______  /_______  //_______  / /_______  / \__/\  / /_______  /
            \/         \/        \/         \/          \/       \/          \/

     -------------------------------------=-----------------------------------
         ROSE SWE                           See ROSEBBS.TXT for
         Dipl.-Ing. Ralph Roth              full address, FAX and PGP keys.
         http://rose.rult.at
         rose_swe@hotmail.com               All Rights Reserved!
     -------------------------------------=-----------------------------------

| Initial Translation by ez-web Digital Services, ezweb@gmx.net in 03/2002

# Computer Viruses and Malware - A Short Overview

A computer virus is a piece of code (software) that is installed on a computer either by a hacker, by another compromised computer (replication), malicious attachments/mails or a website (drive-by infection). It performs functions that the computer owner does not authorize and does not want.

Viruses are sometimes also referred to as malware. This is usually where they have adverse effects on the computer user, such as logging each keystroke (through a keylogger), audio recording or snapshots of each screen.

Such infection can lead to identity theft, endangerment of bank or purchase card data or loss of confidential data. It is more likely to occur on home computers that are normally not as security managed as corporate computers.

## 1. Malware

Malware, or malicious software, is a generic term for a variety of malicious or intrusive software, including computer viruses, worms, Trojans, ransomware (ransoms), spyware, adware, scareware and other malicious programs. It can take the form of executable code, scripts, active content and other software. Malware is defined by its malicious intent, which violates the requirements of the computer user - and therefore does not include software that causes unintentional damage due to a defect.

Programs officially delivered by companies can be considered malware if they secretly violate the interests of the computer user.

## 2. (Computer) Virus

A computer virus is a type of malicious software program ("malware") that, when executed, replicates itself by modifying other computer programs and appending or inserting its own code. When this replication succeeds, the affected programs are then said to be "infected" with a computer virus.

The term "virus" is also commonly, but erroneously, used to refer to other types of malware. "Malware" encompasses computer viruses along with many other forms of malicious software, such as computer "worms", ransomware, spyware, adware, Trojan horses, keyloggers, rootkits, bootkits, malicious Browser Helper Object (BHOs) and other malicious software. The majority of active malware threats are actually Trojan horse programs or computer worms rather than classic computer viruses.

Roughly you can distinguished between - Memory resident (fast) infecting viruses and - Direct action viruses

### 2.1. Direct Action Viruses

Direct action viruses are a type of malware that infect individual files on a computer, rather than the boot sector or Master Boot Record (MBR). They are called "direct action" viruses because they are executed each time a specific file is opened or executed, which allows the virus to infect other files on the computer.

Some of the simpler computer viruses do not actively manifest themselves in computer memory. The very first file infector viruses on the IBM PC, such as Virdem and Vienna, belong to this category. As a rule, direct viruses do not spread quickly and are not easily spread in the wild.

Direct action viruses load themselves into computer memory with the host program. Once they have taken control, they search for new objects to infect by searching for new files. For this very reason, one of the most common types of computer viruses is the direct action infector. This type of virus can be created relatively easily by the attacker in binary or scripting languages on a variety of platforms.

Direct action viruses typically use a FindFirst, FindNext sequence to search for a number of victim applications to attack. Typically, such viruses only infect a few files when executed, but some viruses infect everything at once, enumerating all the directories for victims.

Direct action viruses typically spread by attaching themselves to executable files, such as .exe, .com, or .bat files. When an infected file is executed, the virus infects other files on the computer and may also cause other malicious activity.

### 2.2. (Computer) Boot Virus

Boot viruses are the oldest known computer viruses. They were the most common type of virus until 1995, but are now extinct. Today, there are almost no boot sector viruses anymore because BIOS and operating systems usually have well-functioning software or hardware protection.

A boot virus is a computer virus that becomes active when the computer starts (boots) before the operating system (DOS, Linux or Windows) is fully loaded. Boot sector viruses take advantage of the fact that the boot sector is always loaded first. On floppy disks, the virus is at least partially in the boot sector, so even floppy disks with no files on them can be infected. On hard disks, the virus infects the master boot record (MBR) or logical boot sector.

A boot sector virus infects the boot sector of floppy disks and the master boot record (MBR) of a hard drive. The boot sector is the first physical part of a floppy disk and is a sector (512 bytes). The boot sector is used by boot floppies to boot from the floppy. When a user tries to boot from an infected boot floppy, or leaves an infected floppy in the floppy drive when the computer starts up, the BIOS accesses this sector and executes it with the appropriate BIOS boot setting. The virus then attempts to infect the hard disk’s MBR every time the computer is started. When an infected computer is started, the MBR, which is normally responsible for recognising the different partitions on the hard drive, is loaded. Once loaded, the virus remains in memory and monitors access to floppy disks. When a floppy disc is inserted into a computer infected with a boot sector virus, the virus infects the boot sector of the floppy disc.

Known boot viruses include the Form virus, Parity Boot and Boot-437.

### 2.3. Multipartite Virus

A multipartite virus is a computer virus that infects and spreads in multiple ways. The term was introduced to describe the first viruses that included DOS executable files and PC BIOS boot sector virus code, where both parts are viral themselves. Prior to the discovery of the first of these, viruses were categorized as either file infectors or boot infectors. Because of the multiple vectors for the spread of infection, these viruses could spread faster than a boot or file infector alone.

The first virus that infected COM files and boot sectors, Ghostball (more a dropper than a real multipartite virus), was discovered by Fridrik Skulason in October 1989. Another early example of a multi-part virus was Flip, Frodo, Delwin and Tequila. Tequila for example could infect both DOS EXE files and the MBR (master boot sector) of hard disks.

## 3. Trojan horses

A Trojan horse is a program that does something undocumented which the programmer intended, but that users would not accept if they knew about it. By some definitions, a virus is a particular case of a Trojan horse, namely, one which is able to spread to other programs (i.e., it turns them into Trojans too). According to others, a virus that does not do any deliberate damage (other than merely replicating) is not a Trojan. Finally, despite the definitions, many people use the term "Trojan" to refer only to a non-replicating malicious program.

## 4. Ramsomware

Ransomware is a particularly invasive form of malware that hijacks a victim’s data or device and holds it hostage (or makes false claims of illegal activity, pornography use, or suggests a system is already infected with viruses) until a sum of money is paid to secure its release.

### 4.1. Introduction to Ransomware

Ransomware is a type of malware that hijacks a victim’s data or device, demanding a ransom—usually in cryptocurrency—for its release. Sometimes, it also makes false claims about illegal activity or pre-existing infections to pressure victims. Paying the ransom doesn’t guarantee recovery, as attackers may refuse to decrypt the data or demand more payments. According to Statista, only 54 per cent of organisations regained access to their data or systems after the first payment in 2021. Paying the ransom also encourages attackers to continue their malicious activities. In addition, the vulnerability still exists and can be exploited by another criminal group.

Ransomware has become a global threat, with attacks growing more sophisticated. Understanding its history, evolution, and tactics is critical to combating it.

### 4.2. Origins of Ransomware

Ransomware first appeared in 1989 with the DOS-AIDS Trojan (PC Cyborg), created by Joseph L. Popp. Distributed via floppy disks labeled "AIDS Information," it used simple encryption and demanded $189 for unlocking files.

Popp exploited public fear of the AIDS epidemic to spread the malware. Despite its basic design, many fell victim, incurring financial losses and data breaches. Popp’s erratic behavior led to his arrest, but he was deemed mentally unfit to stand trial. This event set the stage for ransomware to evolve into a significant cybercrime.

### 4.3. Evolution of Ransomware

Ransomware has transformed into a sophisticated, profitable industry:

- Targeted Attacks: Criminals now target high-value victims like corporations, hospitals, and government agencies.

- Stronger Encryption: Modern ransomware uses advanced encryption, making decryption without a key nearly impossible.

- Cryptocurrencies: Bitcoin and Monero enable anonymous payments, fueling ransomware’s growth.

- New Tactics: Techniques like double extortion (encrypting data and threatening leaks) and Ransomware-as-a-Service (RaaS) allow even non-experts to launch attacks.

Notable attacks like WannaCry and NotPetya caused massive global disruptions, targeting businesses and government agencies.

### 4.4. Modern Ransomware Characteristics

Ransomware attacks today are more targeted and damaging:

- Anonymous Payments: Cryptocurrencies make tracking transactions difficult.

- Time Pressure: Deadlines threaten data deletion or leaks, forcing quick victim responses.

- Unreliable Decryption: Many victims don’t recover access, even after paying. In 2021, only 54% regained access after the first payment.

- Encouraging Crime: Paying ransoms perpetuates these attacks and leaves vulnerabilities open for future exploitation.

### 4.5. Steps in a Ransomware Attack

Ransomware attacks follow a common progression:

1. Gaining Access: Attackers infiltrate systems using phishing emails, malware downloads, or exploiting vulnerabilities.

2. Spread: Malware spreads within the network, either automatically or manually in targeted attacks.

3. Hostage Taking: Data is encrypted, and a ransom note demands payment for decryption or preventing data leaks.

### 4.6. Mitigation and Defense

Defending against ransomware requires proactive measures:

- Stay vigilant against phishing attempts and suspicious files.

- Regularly update systems and software to patch vulnerabilities.

- Use multi-factor authentication to secure accounts.

- Maintain offline backups of critical data.

- Invest in robust cybersecurity tools and training.

### 4.7. Ramsonware: Conclusion & Best Practices

Ransomware is an ever-evolving threat. Staying informed and implementing strong defenses can help mitigate the risk and minimize impact.

Ransomware attacks can be extremely damaging and complex, and the timeframe for action is very limited. The best way to deal with them is to avoid them in the first place, and use mechanisms to prevent and mitigate their impact. The best way to prevent a malware attack is to follow good operational and security practices, such as

- Keep all software and operating systems up to date.

- Use anti-virus and anti-malware software on desktop systems.

- Regularly scan for vulnerabilities and comply with security policies, the key is to do this regularly.

- The best way to do this is to automate it so that it does not become a problem and can be integrated as part of the deployment process.

- Ensure that the software supply chain is properly secured. From an attacker’s perspective, attacking the supply chain may be the easiest way to reach most, if not all, of an organisation’s systems.

- Implement proactive measures and adopt a zero-trust policy. This applies to containers as well as traditional environments.

- Implement password validation best practices, such as avoiding common words and using long phrases that are easier for humans to remember but harder for machines to crack.

- Educate staff on basic security principles, such as being wary of suspicious emails, recognising suspicious links and managing data to avoid storing critical data in unsecured locations.

- Perform regular backups and always keep a cold backup in a separate physical location with no network access. Ensure that recovery procedures are tested regularly.

- Automate the provisioning of your infrastructure so that you can restore your systems quickly - time is money.

- Have a disaster recovery plan in place and ensure it is tested regularly.

## 5. Malicious Mining Software (Crypto-Miner)

Starting in 2018 Malware authors are increasingly relying on malicious mining software. This year for the first time there have been more infections of this type than with ransomware. More and more online criminals seem to turn their backs on ransomware and rely on crypto-miner. They secretly dig crypto money on infected computers - Monero is particularly popular. This is obviously extremely lucrative, as the latest figures show.

Reasons for the turnaround? If a ransomware/Trojan strikes and encrypts data from victims, they usually have to pay a ransom in the form of bitcoins. This is an obstacle that not every victim can or will take. Crypto-miner, on the other hand, only needs to infect computers. Afterwards, they dig in secret without any sacrifices and make silently sure that they bring the authors big profits - and not too short when you look at the exploding prices of different crypto currencies.

Nowadays even commercial antivirus software tries to use the user computer when idle for mining. So this kind of software is both a malware scanner and malware itself :-(

## 6. Greyware

Grayware (or greyware) is a general term sometimes used as a classification for applications that behave in a way that is annoying or unwanted, but less serious or problematic than malware. Grayware includes spyware, adware, dialers, joke programs, remote access tools and any other unwanted files and programs other than viruses that are designed to affect the performance of computers. The term has been in use since at least September 2004.

Grayware refers to applications or files that are not classified as viruses or Trojans, but can still affect the performance of computers on the user’s network and pose significant security risks to the user’s business. Grayware often performs a number of unwanted actions, such as annoying users with pop-up windows, tracking user habits and unnecessarily exposing the computer to attacks.

### 6.1. Scam

"Scam is a term used to describe a fraudulent scheme or deception in which someone is tricked into giving away money or personal information. Scams can take many different forms, such as phishing scams, investment scams, lottery scams and technical support scams, to name a few.

Phishing scams are attempts to trick people into revealing sensitive information, such as passwords or credit card numbers, by posing as a trustworthy entity. Investment scams persuade people to invest money in a bogus business or financial scheme with the promise of high returns. Lottery scams are messages informing people that they have won a large sum of money in a lottery, but asking them to pay a small fee or provide personal information to claim the prize. Tech support scams are attempts to trick people into paying for unnecessary computer support services by pretending to be from a reputable tech company.

Scammers often use persuasion and urgency to get people to hand over money or personal information. It is important to be wary of unsolicited messages or offers, and to independently verify the legitimacy of any request for personal information or money. You can protect yourself against fraud by being aware of common scams, being wary of unsolicited messages or offers, and never giving out personal information or money without verifying the identity of the recipient.

### 6.2. Adware

Adware is software that displays advertising banners in web browsers such as Chrome, Internet Explorer and Mozilla Firefox. Although it is not classified as malware, many users find adware invasive. Adware programs often have undesirable effects on a system, such as annoying pop-up ads and general degradation of network connection or system performance. Adware programs are usually installed as separate programs bundled with certain free software from websites. Many users inadvertently agree to install adware by accepting the End User License Agreement (EULA) of the free software. Adware is also often installed together with spyware programs. Both programs benefit from each other’s features - spyware programs profile users' Internet behavior, while adware programs display targeted advertisements that correspond to the collected user profile.

### 6.3. Spyware

Spyware is a type of computer virus that hides on your computer or mobile device, records your private data and sends that information back to whoever created it or monitors it. The tricky thing about spyware, and what separates it from the growing threat of ransomware is the fact that, spyware is designed to both install discretely and operate silently in the background.

Spyware is software that installs components on a computer to record browsing habits (primarily for marketing purposes). Spyware sends this information to its creator or to other interested parties when the computer is online. Spyware is often downloaded along with other components that are referred to as "free downloads" or "freeware" without informing the user about their existence or asking for permission to install them. The information that spyware components collect can include user’s keystrokes (keylogging), which means that private information such as login names, passwords and credit card numbers can be stolen. Spyware collects data, such as account names, passwords, credit card numbers and other confidential information, and transmits it to third parties.

### 6.4. Malvertising

Malvertising, a combination of "malicious" and "advertising", refers to the distribution of malware through online advertising. Cybercriminals use legitimate ad networks to place malicious ads on trusted websites. Users can become infected by clicking on or even just viewing these ads.

How it works

- Inclusion in ad networks: Malicious ads are injected into legitimate networks.

- Spread on websites: These ads appear on popular websites.

- Distribution of malware: Clicking on or viewing the ad can lead to malware infection.

Types of malware

- Ransomware: Encrypts files and holds them for ransom.

- Spyware: Steals confidential information.

- Adware: Displays unwanted advertisements.

- Trojans: Allow unauthorised access to systems.

Protective measures

- Ad blockers: Prevent malicious ads from loading.

- Updated software: Reduces risks from known vulnerabilities.

- Security software: Antivirus programs and firewalls provide protection.

- Be careful what you click: Avoid clicking on suspicious ads.

## 7. Backdoors

A point of access to a hidden program/system. Backdoors are usually intentionally created by a programmer for debugging or maintenance purposes, but if compromised, they can pose a security risk to unauthorized users or software, allowing access and causing damage. Malware often installs Backdoors on compromised systems!

## 8. Botnets

A bot is a programs that run automated tasks over the Internet. Botnets are collection of bots that run autonomously and automatically. Typically they perform repetitive tasks at a much higher rate than a human is capable of. They can be used for malicious purposes, such as denial of service attacks or infecting other computers. An infected computer is called a bot or zombie.

## 9. Macro viruses

A macro is a piece of code that can be embedded in a data file. A macro virus is thus a virus that exists as a macro attached to a data file. In most respects, macro viruses are like all other viruses. The main difference is that they are attached to data files (i.e., documents) rather than executable programs. Document-based viruses are, and will likely continue to be, more prevalent than any other type of virus.

## 10. Worms

Worms are very similar to viruses in that they are computer programs that replicate functional copies of themselves (usually to other computer systems via network connections) and often, but not always, contain some functionality that will interfere with the normal use of a computer or a program. Unlike viruses, however, worms exist as separate entities; they do not attach themselves to other files or programs. Because of their similarity to viruses, worms also are often referred to as viruses.

## 11. Protestware

In March 2022, a developer of node-ipc was caught adding malicious code to the popular open source package that deleted files on computers in Russia and Belarus. This was part of a protest that angered many users and raised concerns about the security of free and open source software. The node-ipc update is just one example of what some researchers call protestware. Most protest programs related to the Russian invasion of Ukraine simply display anti-war and pro-Ukrainian messages. However, in at least one project, virus-like code was added that aimed to cripple computers in Russia and Belarus. This led to criticism and accusations of causing collateral damage. But there are also examples of protest in the open source scene. Observers of the scene so far found about two dozen software projects that inserted "code against war."

Open-source programs can be modified and viewed by anyone, making them more transparent - and, at least in this case, more vulnerable to sabotage. The protestware event highlights some of the risks that arise when legions of volunteer developers create the code that is critical to running hundreds or thousands of other applications. Some open source software automatically downloads and integrates new versions, and even for those that don’t, the vast amount of code often makes manual review infeasible. This means that an update by a single person can mess up an untold number of downstream applications. In that sense, this can be considered a "game changer."

Russia’s largest bank has asked its customers to stop updating its software because it is under threat from "protestware". In response to the threat, Russian state-owned bank Sberbank even advised its Russian customers to manually check the source code of the software they need - a security measure that is not feasible for most users. "We urge users to stop updating software and developers to tighten monitoring when using external code," Sberbank said, according to Russian media and cybersecurity firms.

## 12. Stealth viruses

What is a stealth virus? A stealth virus is one that, while active, hides the modifications it has made to files or boot records. It usually achieves this by monitoring the system functions used to read files or sectors from storage media and forging the results of calls to such functions. This means that programs that try to read infected files or sectors see the original, uninfected form instead of the actual, infected form. Thus the virus’s modifications may go undetected by antivirus programs. However, in order to do this, the virus must be resident in memory when the antivirus program is executed, and the antivirus program may be able to detect its presence.

The very first DOS virus, Brain, a boot-sector infector for example monitored physical disk input/output and redirected any attempt to read a Brain-infected boot sector to the disk area where the original boot sector was stored.

### 12.1. File stealth viruses

In addition to hiding the boot information, DOS file stealth viruses attack .com and .exe files when opened or copied, and hide the file size changes from the DIR command. The major problem arises when you try to use the CHKDSK/F command and there appears to be a difference in the reported files size and the apparent size. CHKDSK assumes this is the result of some cross-linked files and attempts to repair the damage. The result is the destruction of the files involved.

### 12.2. Full stealth viruses

With a full stealth virus, all normal calls to file locations are cached, while the virus subtracts its own length so that the system appears clean.

### 12.3. Countermeasures against Stealth Viruses?

You need a clean system so that no virus is present to distort the results of system status checks. Thus you should start the system from a trusted, clean, bootable diskette before you attempt any virus checking.

## 13. Encryption

One method of evading malware detection is to use simple encryption to encipher (encode) the body of the malware, leaving only the encryption module and a static cryptographic key in clear text which does not change from one infection to the next.

### 13.1. What is a polymorphic virus?

A polymorphic virus is one that produces varied but operational copies of itself. This strategy assumes that virus scanners will not be able to detect all instances of the virus. One method of evading scan-string driven virus detectors is self-encryption with a variable key. Polymorphic code was the first technique that posed a serious threat to virus scanners.

More sophisticated polymorphic viruses (e.g., V2P6) vary the sequences of instructions in their variants by interspersing the decryption instructions with "noise" instructions (e.g., a No OPeration instruction (NOP), or an instruction to load a currently unused register with an arbitrary value), by interchanging mutually independent instructions, or even by using various instruction sequences with identical net effects (e.g., Subtract A from A, and Move 0 to A). A simple-minded, scan-string based virus scanner would not be able to reliably identify all variants of this sort of virus; in this case, a sophisticated scanning engine has to be constructed after thorough research into the particular virus.

One of the most sophisticated forms of polymorphism used so far is the Mutation Engine (MtE) or the Trident Polymorph Engine (TPE), which comes in the form of an object module. With such mutation engines, any virus can be made polymorphic by adding certain (API) calls to its assembler source code and linking to the mutation-engine and provided random-number generator modules.

The advent of polymorphic viruses has rendered virus scanning an increasingly difficult and expensive endeavor; adding more and more search strings to simple scanners will not adequately deal with these viruses.

## 14. What is an armored virus?

Armored viruses use special tricks to make the tracing, disassembling, and understanding of their code more difficult. A good example is the Whale virus. An armored virus uses various techniques to evade detection, such as encrypting its code, obfuscating its code, and using anti-debugging and anti-tampering methods.

Armored viruses pose a serious threat because they can be used to perform malicious activities such as stealing sensitive information, altering or corrupting data, and slowing performance without being detected. They can also be used as part of more complex attacks, such as advanced persistent threats (APTs), to maintain a foothold on a target network over an extended period of time.

## 15. What is Phishing/Vishing?

Phishing and vishing are types of scams used to steal sensitive information such as passwords, credit card numbers and other personal data.

Phishing is a type of scam that tricks people into providing sensitive information through fake emails or websites that appear to be from a reputable source, such as a bank or a well-known company. The goal of phishing scams is to trick people into revealing personal information, such as passwords or credit card numbers, by posing as a trustworthy entity.

Vishing, short for voice phishing, is a type of phishing scam where people are tricked into revealing sensitive information over the phone. In vishing scams, scammers often pretend to be from a bank, government agency or technology company and use persuasive techniques to get people to reveal sensitive information.

Both phishing and vishing scams are becoming increasingly sophisticated and it is important to be wary of unsolicited emails or phone calls. To protect yourself from these types of scams, never provide sensitive information in response to an unsolicited request and independently verify the identity of the recipient before providing any personal information.

## 16. Secure Boot/UEFI/Firmware Malware

In 2012, an industry-wide coalition of hardware and software makers adopted Secure Boot as a crucial defense mechanism against a growing and sophisticated security threat: malware targeting the system’s firmware, specifically the BIOS. The BIOS, or Basic Input/Output System, is the firmware responsible for initializing hardware components and loading the operating system every time a computer is powered on. Malware that infects the BIOS poses an especially insidious threat because it can establish a foothold deep within the system, evading traditional detection methods and persisting through operating system reinstalls. Once entrenched, such malware can execute before the operating system and any security software, making it extremely difficult to detect and remove.

The threat of BIOS-dwelling malware had long been considered theoretical, heightened by the creation of the ICLord BIOS rootkit by a Chinese researcher in 2007. ICLord was a proof-of-concept rootkit, a type of malware designed to gain and maintain privileged access to a system while remaining hidden from standard security measures. This proof of concept not only demonstrated the feasibility of BIOS rootkits but also underscored their potential power. While ICLord remained a theoretical threat, it set the stage for the realization of more dangerous malware.

In 2011, the landscape of firmware security changed dramatically with the discovery of Mebromi, the first-known BIOS rootkit to be observed in the wild. Mebromi marked the transition from theoretical to actual threat, underscoring the vulnerability of BIOS firmware to sophisticated attacks. Mebromi was capable of infecting the BIOS, overwriting it with malicious code, and maintaining persistence even after the operating system was reinstalled—a stark reminder of the critical need for stronger security measures.

Recognizing the severity of the threat posed by Mebromi and other potential firmware attacks, the architects of Secure Boot developed a sophisticated security framework aimed at fortifying the pre-boot environment. Integrated into the Unified Extensible Firmware Interface (UEFI)—which was designed to replace the aging BIOS system—Secure Boot leverages public-key cryptography to verify the integrity and authenticity of firmware and software components before they are loaded. Specifically, Secure Boot only allows the execution of code that is signed with a recognized and trusted digital signature, effectively preventing unauthorized or malicious code from compromising the system at such an early and vulnerable stage.

To this day, Secure Boot is regarded by security experts and organizations—including Microsoft and the US National Security Agency—as a foundational element in protecting devices, particularly in critical environments such as industrial control systems and enterprise networks. Its role in establishing a chain of trust from the hardware through to the operating system is considered essential in defending against the sophisticated and persistent malware threats that continue to evolve. The adoption of Secure Boot represents a significant milestone in the ongoing effort to enhance cybersecurity and protect against the increasingly complex landscape of malware attacks.

In 2024 Secure Boot is considered to be broken because cryptografic keys to protect secure boot were leaked (PKfail)

### 16.1. UEFI Bootkits in General

UEFI bootkits are a type of malware that hides in the UEFI firmware of a computer. UEFI is a software program that controls the boot process of boot process and execute malicious code before the operating system even starts.

- UEFI bootkits are difficult to detect and remove because they hide in the UEFI firmware.

- UEFI bootkits can be used to install persistent malware that remains active even after the operating system is reinstalled.

- UEFI bootkits can be used to steal sensitive data, such as passwords and bank details.

Countermeasures:

- Enable UEFI Secure Boot to prevent unauthorized code from running during the boot process.

- Keep your system firmware and operating system up to date to patch vulnerabilities.

- Use reliable antivirus software to detect and remove UEFI bootkits.

### 16.2. Rootkits and Bootkits

Rootkits and bootkits are sophisticated forms of malware that compromise system integrity by gaining unauthorized control over devices. Operating at low levels within an operating system or firmware, they are particularly challenging to detect and remove. This document outlines their functionality, types, techniques, and strategies for mitigation.

- Rootkits are tools that allow attackers to gain and maintain privileged access to a system while concealing their presence.

- Bootkits are a specific type of rootkit that infects the boot process, compromising systems before the operating system loads.

Both rootkits and bootkits pose significant security risks due to their stealthy operations and privileged access capabilities. Both rootkits and bootkits often conceal their presence by altering system internals. Traditional antivirus solutions may struggle to detect them due to their low-level operations.

Rootkits and bootkits represent significant threats to modern computing environments due to their stealthy nature and privileged access capabilities. Effective detection and mitigation require robust security practices, including hardware-based protections, monitoring tools, and proactive patching. Understanding these threats is essential for safeguarding critical systems and sensitive data.

## 17. Links / Pointers

https://en.wikipedia.org/wiki/Timeline_of_computer_viruses_and_worms

## 18. Some very old (DOS) viruses that were very widespread in the past

MS-DOS viruses were particularly prevalent during the early days of personal computing, exploiting the relatively limited security measures of that era. Here are some notable MS-DOS viruses:

# CIH (Chernobyl) - Origin: Taiwan, 1998 - Type: File virus - Description: Known for its destructive payload that triggered on April 26, it could overwrite critical parts of the BIOS, rendering computers unbootable. Although not an MS-DOS virus, it affected Windows 9x systems that were based on DOS.

# Sasser - Origin: Germany, 2004 - Type: Worm - Description: While not strictly an MS-DOS virus, Sasser exploited vulnerabilities in Windows systems to spread. It caused widespread disruptions in the early 2000s.

# Melissa - Origin: USA, 1999 - Type: Macro virus - Description: This virus spread through Microsoft Word documents and email, causing substantial email server disruptions. While primarily a macro virus, its impact was significant across various Windows environments.

# Lehigh - Origin: USA, 1987 - Type: Boot sector virus - Description: One of the early boot sector viruses, it specifically targeted the master boot record and could corrupt the entire hard disk.

# Form - Origin: Probably Swiss, early 1990s - Type: Boot sector virus - Description: This virus became widely known for its payload that activated on the 18th of each month, causing the keyboard to behave erratically.

# Elk Cloner - Origin: USA, 1982 - Type: Boot sector virus (on Apple II, not MS-DOS, but historically significant) - Description: One of the earliest known viruses, it displayed a poem on the 50th boot of an infected system. Although not an MS-DOS virus, it is significant in the history of computer viruses.

# Ping Pong (Bouncing Ball) - Origin: Italy, 1988 - Type: Boot sector virus - Description: This virus caused a bouncing ball effect on the screen and infected the boot sector of floppy disks.

These viruses highlight the diverse strategies employed by malware developers in the MS-DOS era, from boot sector infections to file-based and polymorphic techniques, illustrating the early challenges of computer security.

# The Brain Virus: The Birth of the Computer Virus Era

The Brain virus, often cited as the first IBM PC-compatible virus, marked a significant milestone in the history of computer security. Created in 1986 by two brothers in Pakistan, it initiated an era of growing cybersecurity threats and responses.

The Brain virus was developed by Basit and Amjad Farooq Alvi, who operated a computer store in Lahore, Pakistan. Frustrated with the piracy of their medical software, they created the virus as a form of copy protection, embedding their contact information within the code to raise awareness about piracy.

The Brain virus serves as a historical landmark in cybersecurity, highlighting the early challenges of digital security and the unintended consequences of technological interventions. It underscored the need for ongoing vigilance and education in the evolving landscape of cybersecurity.

## Technical Details

The Brain virus is a boot sector virus, infecting the boot sector of storage media like floppy disks. It becomes resident in memory when the computer boots from an infected disk and then infects any clean disks accessed by the system. It displays a message with the authors' names and contact details, an unusual feature among viruses.

Infection Mechanism:

- Boot Process: Loads into memory during boot from an infected disk.

- Replication: Spreads to other disks accessed by the infected computer.

- Infected Message: Displays a message with the creators' contact information.

Attributes:

- Memory Resident: Remains active until the computer is turned off.

- Stealth Techniques: Hides its presence by intercepting system calls.

- Non-Destructive: Does not delete or corrupt files, focusing instead on spreading and delivering a message.

## Impact and Spread

The Brain virus’s impact was significant, as it was the first widely recognized PC boot virus. It spread rapidly through the common practice of sharing floppy disks, reaching users worldwide by the late 1980s.

Geographical Spread:

- Local to Global: Initially spread within Pakistan, then globally through shared software.

Economic and Social Impact:

- Awareness and Fear: Raised awareness about computer security and vulnerabilities.

- Economic Consequences: Prompted investments in antivirus software and improved security practices.

### 18.1. Cascade

Cascade virus (also known as Herbstlaub in Germany) is a well-known DOS computer virus that is a memory-resident virus written in assembly language. Cascade was widely spread in the 1980s and early 1990s. It infected DOS .COM files and caused the text on the screen to cascade down and form a pile at the bottom of the screen. It was notable for the fact that it used an encryption algorithm to avoid detection. However, it could be seen that the size of the infected files increased by 1701 or 1704 bytes. In response, IBM developed its own anti-virus software.

When a file infected with Cascade is introduced into a system and executed, the virus checks the BIOS for the string "COPR. IBM", an IBM copyright notice in the BIOS. If it finds the string, it tries to stop there, but fails, and the virus becomes memory resident. Every time a .COM file is executed, the virus starts infecting it. It replaces the first three bytes of the new host file with code that references the virus code. The virus places the original first three bytes of the host into its own code.

Cascade’s payload is executed when an infected file is executed between October 1 and December 31, 1988. It causes characters on a DOS screen to randomly drop down in a pile of numbers and letters. Variants can also cause noise.

The virus has a number of variants. Cascade-17Y4, which is believed to have originated in Yugoslavia, is almost identical to the most common 1704-byte variant. One byte has been changed, probably by a random "mutation". However, this has resulted in a "bug" in the virus. Another mutated variant is also known - it infects the same file over and over again.

### 18.2. Jerusalem

Jerusalem is a DOS virus which was first detected in Jerusalem in October 1987. Its origin is uncertain, as it was thought to have originated in Israel, but evidence from 1991 suggests that it may have originated in Italy. As of 1993, Jerusalem was still in the wild and many variants had been created. The last reported case of Jerusalem was in 1995, almost 8 years after its discovery. The virus has gone by many names, some referring to its possible origin and its Friday the 13th payload date. Jerusalem was initially very common (for a virus at the time) and spawned a large number of variants. However, since the advent of Windows, these DOS interrupts are no longer used, so Jerusalem and its variants have become obsolete.

Once infected, the Jerusalem virus becomes memory resident (using 2kb of memory) and then infects every executable file that is run, except for COMMAND.COM. COM files grow by 1,813 bytes when infected by Jerusalem and are not re-infected. EXE files grow between 1,808 and 1,823 bytes each time they are infected. The virus re-infects .EXE files each time they are loaded until they are too large to load into memory. Some .EXE files are infected but do not grow because multiple overlays follow the real .EXE file in the same file. Sometimes .EXE files are infected by mistake, so that the programme fails to run when it is run.

The virus code itself hooks into interrupt processing and other low level DOS services. For example, code in the virus suppresses the printing of console messages if, for example, the virus is not able to infect a file on a read-only device such as a floppy disk. One of the clues that a computer is infected is the mis-capitalization of the well-known message "Bad command or file name" as "Bad Command or file name".

The program contains one destructive payload that is set to go off on Friday the 13th, all years but not in 1987. On that date, the virus deletes every program file that was executed. Jerusalem is also known as BlackBox because of a black box it displays during the payload sequence. If the system is in text mode, Jerusalem creates a small black rectangle from row 5, column 5 to row 16, column 16. The rectangle is scrolled up by two lines.

As a result of the virus hooking into the low-level timer interrupt, PC-XT systems slow down to one fifth of their normal speeds 30 minutes after the virus has installed itself. The slowdown is less noticeable on faster machines. The virus contains code that enters a processing loop each time the processor’s timer tick is activated.

Symptoms also include spontaneous disconnection of workstations from networks and creation of large printer spooling files. Disconnections occur since Jerusalem uses the interrupt 21h low-level DOS functions that Novell Netware and other networking implementations required to hook into the file system.

Variants

Over the years that Jerusalem spread, many virus coders created variants of the virus, making Jerusalem one of the largest families of viruses ever created. It even includes many sub-variants and a few sub-sub-variants. Most variants are unimaginative, simply changing the payload date, text displayed or even nothing at all. Some variants contain fixes for the bugs of the original.

    Jerusalem.1013 Jerusalem.1024 Jerusalem.1234 Jerusalem.1237 Jerusalem.1238
    Jerusalem.1241 Jerusalem.1244 Jerusalem.1264 Jerusalem.1291 Jerusalem.1329
    Jerusalem.1347 Jerusalem.1348 Jerusalem.1349 Jerusalem.1353 Jerusalem.1356
    Jerusalem.1361 Jerusalem.1363 Jerusalem.1364 Jerusalem.1390 Jerusalem.1399
    Jerusalem.1408 Jerusalem.1427 Jerusalem.1446 Jerusalem.1448 Jerusalem.1455
    Jerusalem.1459 Jerusalem.1477 Jerusalem.1478 Jerusalem.1487 Jerusalem.1488
    Jerusalem.1489 Jerusalem.1500 Jerusalem.1503 Jerusalem.1504 Jerusalem.1511
    Jerusalem.1518 Jerusalem.1521 Jerusalem.1522 Jerusalem.1523 Jerusalem.1524
    Jerusalem.1525 Jerusalem.1526 Jerusalem.1530 Jerusalem.1533 Jerusalem.1536
    Jerusalem.1548 Jerusalem.1552 Jerusalem.1558 Jerusalem.1562 Jerusalem.1568
    Jerusalem.1570 Jerusalem.1587 Jerusalem.1589 Jerusalem.1591 Jerusalem.1596
    Jerusalem.1598 Jerusalem.1605 Jerusalem.1607 Jerusalem.1624 Jerusalem.1631
    Jerusalem.1639 Jerusalem.1640 Jerusalem.1653 Jerusalem.1664 Jerusalem.1682
    Jerusalem.1692 Jerusalem.1715 Jerusalem.1716 Jerusalem.1720 Jerusalem.1721
    Jerusalem.1728 Jerusalem.1733 Jerusalem.1735 Jerusalem.1747 Jerusalem.1756
    Jerusalem.1765 Jerusalem.1767 Jerusalem.1768 Jerusalem.1783 Jerusalem.1792
    Jerusalem.1807 Jerusalem.1808 Jerusalem.1813 Jerusalem.1824 Jerusalem.1845
    Jerusalem.1884 Jerusalem.1888 Jerusalem.1899 Jerusalem.1960 Jerusalem.1968
    Jerusalem.1970 Jerusalem.1975 Jerusalem.1984 Jerusalem.1991 Jerusalem.2000
    Jerusalem.2012 Jerusalem.2027 Jerusalem.2053 Jerusalem.2064 Jerusalem.2080
    Jerusalem.2082 Jerusalem.2083 Jerusalem.2116 Jerusalem.2126 Jerusalem.2128
    Jerusalem.2132 Jerusalem.2187 Jerusalem.2208 Jerusalem.2223 Jerusalem.2224
    Jerusalem.2272 Jerusalem.2291 Jerusalem.2350 Jerusalem.2358 Jerusalem.2368
    Jerusalem.2389 Jerusalem.2437 Jerusalem.2465 Jerusalem.2472 Jerusalem.2490
    Jerusalem.2576 Jerusalem.2758 Jerusalem.2880 Jerusalem.2886 Jerusalem.3887
    Jerusalem.4112 Jerusalem.5120 Jerusalem.641 Jerusalem.662 Jerusalem.679
    Jerusalem.878 Jerusalem.880 Jerusalem.986 Jerusalem.A Jerusalem.CVEX
    Jerusalem.Curse Jerusalem.June11_T3Scan Jerusalem.Plastique
    Jerusalem.Roger Jerusalem.a Jerusalem.com Jerusalem.sURIV_3

# The Tequila Virus

It was one of the early examples of a polymorphic virus, making it harder to detect by antivirus software because it changed its code each time it infected a new file. The Tequila virus, originating in Switzerland in 1991, is one of the earliest examples of polymorphic malware. This advanced virus significantly impacted the evolution of malware and cybersecurity strategies by evading detection through code mutation.

## Technical Details

The Tequila virus infected executable (.EXE) files on DOS-based systems. It was a memory-resident virus that used polymorphism to alter its code with each new infection, making it difficult for signature-based antivirus programs to detect it.

Infection Mechanism:

1. File Infection: Attaches to executable files, embedding its encrypted code.

2. Memory Residency: Becomes resident in memory upon execution of an infected file, allowing it to infect other executables.

3. Polymorphism: Uses a mutation engine to change its code with each infection, evading detection.

Technical Attributes:

- Encryption: Hides its presence within infected files using encryption.

- Mutation Engine: Alters its code with each infection, complicating detection.

- Payload: Displays a fractal, alerting users to its presence.

Tequila pioneered polymorphic techniques, influencing future malware development and antivirus strategies. The Tequila virus was a landmark in the history of computer viruses, demonstrating sophisticated polymorphic techniques that challenged and shaped the development of antivirus technologies and cybersecurity strategies.

### 18.3. Stoned

The Stoned Virus Family: A Legacy of Boot Sector Infections

Stoned is a very large family of boot sector viruses on the DOS platform, originating in early 1988. This family of viruses became infamous for its persistent and insidious nature, with notable members such as the Michelangelo virus, which incited widespread panic in the early 1990s, and the Angelina virus from 1994, which notably resurfaced on infected laptops as late as 2007. The Stoned virus was allegedly created by a student at the University of Wellington in New Zealand.

## Mechanism of Infection

When a computer boots from an infected hard drive, Stoned becomes resident in memory, establishing a foothold in the system. If the computer boots from a disk other than the hard disk, Stoned checks the master boot record (MBR) of the hard disk and infects it if it is clean.

- Floppy Disk Infection: When infecting a floppy disk, Stoned relocates the master boot record to sector 11 and places its own code in sector 0.

- Hard Disk Infection: When infecting the hard disk, it moves the MBR to page 0, cylinder 0, sector 7, and places itself in page 0, cylinder 0, sector 1.

The original variant of the Stoned virus targets only 360-kilobyte 5.25-inch floppy disks and hard disks.

Once resident in memory, Stoned infects the MBRs of all accessed floppy disks but does not reinfect the hard disk. Even if the virus is removed from the MBR while it is still in memory, it does not attempt to reinfect the hard disk.

## Payload and Effects

The Stoned virus has a 1 in 8 chance of releasing its payload during the boot process. When this happens, the infected computer emits a beep and displays the following message:

``` Your PC is now stoned! LEGALIZE MARIJUANA! ```

## Prominent Members

1. Michelangelo Virus: This variant caused significant panic in the early 1990s. Despite the media hype, it infected only a few thousand computers, demonstrating how fear and misinformation can amplify perceived threats.

2. Angelina Virus: Identified in 1994, this variant became notable again in 2007 when it was discovered on laptops that had been sold with pre-existing infections. This resurgence highlighted the enduring nature of some viruses and the importance of rigorous cybersecurity measures.

## Legacy and Impact

The Stoned virus family exemplifies the early challenges of cybersecurity and the evolving nature of computer threats. Despite its relatively simple mechanics by today’s standards, the impact of the Stoned virus family was profound, illustrating the vulnerabilities in early computing systems and the significant role of media in shaping public perception of cybersecurity threats.

### 18.4. Michelangelo

Michelangelo Virus: A Case of Media-Driven Panic

The Michelangelo virus, which stems from the Stoned boot virus family, is renowned for being one of the first computer viruses to garner widespread media attention. While it incited substantial panic, the actual damage it inflicted was minimal. The virus infected only a few thousand computers, making it a classic example of media-induced hysteria.

The media frenzy began in January 1992 when two coincidental events sparked interest. One computer manufacturer inadvertently shipped 500 computers infected with the Michelangelo virus. On the same day, another manufacturer announced it would begin shipping computers with pre-installed antivirus software. This concurrence captured the media’s attention, leading to a flurry of sensationalist reporting.

United Press International played a pivotal role in escalating the panic by interviewing key figures in the cybersecurity field. Among them was the International Partnership Against Computer Terrorism and John McAfee, the president of a prominent antivirus company. These interviews fueled fears, with projections suggesting that hundreds of thousands of computers could be destroyed by the virus. Data recovery consultant Martin Tibor further amplified concerns with dramatic statements like "I find virus disasters everywhere" and "I see victims of viruses all the time."

In the weeks leading up to the virus’s activation date, the media focused heavily on the potential local impact. Some outlets chose to report more on the growing hysteria than on factual information about the virus itself. Few took the initiative to consult with real experts to mitigate the panic. As a result, a significant number of computer users rushed to purchase antivirus software, driven by the fear of imminent digital disaster.

In hindsight, the Michelangelo virus serves as a poignant reminder of the power of media in shaping public perception and the importance of critical evaluation of such reports. While the virus itself was relatively harmless, the surrounding hype created a disproportionate sense of urgency and fear among computer users.

/* End of Document */