Parent class: VirWare

Viruses and worms are malicious programs that self-replicate on computers or via computer networks without the user being aware; each subsequent copy of such malicious programs is also able to self-replicate. Malicious programs which spread via networks or infect remote machines when commanded to do so by the “owner” (e.g. Backdoors) or programs that create multiple copies that are unable to self-replicate are not part of the Viruses and Worms subclass. The main characteristic used to determine whether or not a program is classified as a separate behaviour within the Viruses and Worms subclass is how the program propagates (i.e. how the malicious program spreads copies of itself via local or network resources.) Most known worms are spread as files sent as email attachments, via a link to a web or FTP resource, via a link sent in an ICQ or IRC message, via P2P file sharing networks etc. Some worms spread as network packets; these directly penetrate the computer memory, and the worm code is then activated. Worms use the following techniques to penetrate remote computers and launch copies of themselves: social engineering (for example, an email message suggesting the user opens an attached file), exploiting network configuration errors (such as copying to a fully accessible disk), and exploiting loopholes in operating system and application security. Viruses can be divided in accordance with the method used to infect a computer:
  • file viruses
  • boot sector viruses
  • macro viruses
  • script viruses
Any program within this subclass can have additional Trojan functions. It should also be noted that many worms use more than one method in order to spread copies via networks.

Class: Virus

Viruses replicate on the resources of the local machine. Unlike worms, viruses do not use network services to propagate or penetrate other computers. A copy of a virus will reach remote computers only if the infected object is, for some reason unrelated to the virus function, activated on another computer. For example: when infecting accessible disks, a virus penetrates a file located on a network resource a virus copies itself to a removable storage device or infects a file on a removable device a user sends an email with an infected attachment.

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Platform: DOS

No platform description


Technical Details

These are dangerous memory-resident encrypted parasitic stealth viruses. They infect, in a standard way, COM, EXE and OVL files whenever they are started or closed.

This virus hooks and handles 16 functions of the 21h interrupt. This virus creates the file "C:FISH-#9.TBL," into which it writes the hard-disk MBR and the following phrase:

"FISH VIRUS #9 A Whale is no Fish! Mind her Mutant Fish and the hidden Fish
Eggs for they are damaging. The sixth Fish mutates only if Whale is in her
From February 19th until March 10th, the virus hangs up the system, and displays the following string:
It is very difficult to analyze this virus, because all 9Kb of its code are full of program traps hampering a trace, disassembling and analysis the virus. If the virus listing is to be printed, you should check a dozen special programming methods (dynamic de/enciphering, dummies, use of conveyor, code cipher nesting and so on). As a file is infected, the encrypted virus body is written to it so as a decipher should check 30 variants. That is, you have to use 30 masks to find the virus in the file.

The virus also contains the strings: "THE WHALE", "5HS5IF", "5IF5HS". It hooks INT 9, 21h.

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