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: Linux

Linux is a family of UNIX-influenced operating systems based on the Linux kernel and GNU tools.


Technical Details

Alaeda is a non-resident virus. It infects systems running Linux, and is written in Assembler. It infects ELF format files in the current directory.

When infecting, the virus modifies the entry point of the original file, passing control to the infection routine. It modified the file's ELF header. Before infecting, the victim machine will be checked to see if it can be infected. The .text section of the file to be infected must be of a minimum size for malicious code to be injected.

The virus writes its body to the .text section; the size of the infected file will not change, making it harder to detect infection.

Once the virus body has delivered its payload, control is returned to the program code.

Repeat infection of an already infected file is prevented by a "!" flag placed in a reserved, unused byte which is not used by the interpreter in the ELF header at offset Fh.

The following strings can be found in infected files:

AL-QAEDA 1-02-032
With help of Allah I will die for Allah

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