The Koobface virus which Kaspersky Lab reported in July this year has hit again, and is targeting Facebook users. The worm is designed to upload malicious modules via the Internet, and spreads easily among users.

Kaspersky Labs explained that the worm creates spam messages and sends them to the infected users’ friends on Facebook. Furthermore, the messages and comments on Facebook include links to a malicious site, which prompts the user to download the latest version of Adobe Flash, instead downloading the file codecsetup.exe into the user’s computer.

Furthermore, the same problem was also reported for MySpace users, and the worm was described as a network worm, meaning that users who have come to the site via Facebook will have the MySpace worm downloaded to their machines, and vice versa.

Considering its way of spreading, the users are very likely to become victims, especially since it is targeting a social networking site.

“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”, Alexander Gostev, Senior Virus Analyst at Kaspersky Lab, noted in July.

According to a Facebook spokesperson, only a small percentage of users have been affected, and they are currently working on updating their security systems to minimize the impact.

Security researchers still know very little about who may have started the attack. The phenomenon is even harder to contain if users are not paying more attention to the messages they open, to the links they follow or to the downloads they make.