Net-Worm.Win32.Koobface.a. and Net-Worm.Win32.Koobface.b, attack MySpace and Facebook respectively, say security firm Kaspersky Lab, which found the threats.
The worms are designed to upload malicious modules with other functionality via the web. It's likely that they will turn target machines into zombie computers to form botnets.
Net-Worm.Win32.Koobface.a spreads when a user accesses their MySpace account and creates a range of comments that are sent to friends' accounts. On Facebook, Net-Worm.Win32.Koobface.b creates spam messages and sends them to the infected users' friends on the website.
Headlines such as “Paris Hilton Tosses Dwarf On The Street” and “Examiners Caught Downloading Grades From The Internet” are typically used to encourage users to click on a bogus video link that tells them to download a so-called new version Flash Player that is a disguise for codesetup.exe, which installs malware.
Alexander Gostev, senior virus analyst at Kaspersky Lab, said: “Unfortunately, users are very trusting of messages left by ‘friends' on social networking sites. So the likelihood of a user clicking on a link like this is very high.
“At the beginning of 2008 we predicted that we'd see an increase in cybercriminals exploiting MySpace, Facebook and similar sites, and we're now seeing evidence of this. I'm sure that this is simply the first step, and that virus writers will continue to target these resources with increased intensity”.
It is highly probable that victim machines will not only be used for spreading links via these social networking sites, but the botnets will also be used for other malicious purposes, added a statement on the Kaspersky site.