Class
Worm
Platform
DOS

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: Worm

Worms spread on computer networks via network resources. Unlike Net-Worms, a user must launch a Worm in order for it to be activated. This kind of worm searches remote computer networks and copies itself to directories that are read/write accessible (if it finds any). Furthermore, these worms either use built-in operating system functions to search for accessible network directories and/or they randomly search for computers on the Internet, connect to them, and attempt to gain full access to the disks of these computers. This category also covers those worms which, for one reason or another, do not fit into any of the other categories defined above (e.g. worms for mobile devices).

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Platform: DOS

No platform description

Description

Technical Details

These are not dangerous memory resident encrypted stealth virus-worms. Being executed they display the messages:

"Worm.Info.2142":

-*-  INFOSYSTEM  -*-
version 1.04
(C) 1995 by Ziff Co.
Reading System Information...
Computer type: IBM PC

"Worm.Info.2191":

InfoSystem  version1.01
Reading System Information...
Computer type: IBM PC

"Worm.Info.2259":

Reading System Information...
Computer type: IBM PC

then they check the type of computer and display one of the strings:

Original
XT
AT
Convertible
PS/2
Junior
Unknown

Then the virus displays the messages:

Checking HDD controller...
SCSI controller type: Unknown (Error14)

and calls the infection routine. While infecting the computer the virus searches for directories that are listed in PATH string, creates there INFO.COM files, and writes its code into there. Then the virus searches for .BAT files in these directories and writes the commands:

@if not exist info.com goto noinfo
@info>nul
:noinfo

to the beginning of batch files. Being executed such BAT files run the virus.

Then the virus installs itself memory resident into UMB, HMA or conventional memory, hooks INT 1Ch, 21h and then drops its code into current directories on FindFirst (AH=11h,4Eh) calls. On accessing to modified BAT files, and on FindFirst/Next calls the virus calls stealth routine. The virus also checks the name of the programs that are executed, and if the name is CHDDSK, WEB or DRWEB the virus disables its stealth routines.

By hooking INT 1Ch the virus checks INT 1 vector (tracing) and disables tracing the virus code.

On Friday 13th the virus changes the VGA video ports.

The virus also contains the internal text strings:

COMMAND NET?.CHKDSK.WEB.DRWEB.INFO.COM ATH=*.BAT

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