Microsoft’s Malware Protection Centre has described two families of PC virus that actually work together to download new versions of the viruses, making them harder to eradicate. Called Vobfus and Beebone, one works to download new versions of the other.
Vobfus is usually the first infection, arriving through fake links, infected USB drives or across networked PCs. This then downloads Beebone, which enlists your PC in a botnet – with all the other Beebone infected computers. Beebone can then download fresh versions of the Vobfus virus.
The advantage of this collaboration for the viruses is that they may be able to stay ahead of malware detection. You could discover a known version of one virus on your PC, but it might have already downloaded a newer version of the other which has not yet been detected.
Microsoft recommend making sure your browser is always up to date, which helps prevent you from visiting potentially dangerous sites. Disabling ‘autorun’ on Windows XP is also a good way to avoid viruses installing themselves from infected drives. You should always make sure your antivirus suite is up to date.
[Source: Malware Protection Centre]