Users of social-networking sites have been warned to be alert after Facebook was targeted by a virus known as “Koobface.” The Koobface video virus utilizes the social network’s messaging system to infect computer system and then attempts to gather sensitive data such as credit card numbers. It is the latest attack by hackers looking to profit from the success of social-networking websites where e-mails and messages appearing to be coming from friends are more likely to be opened, exposing the user to the virus. Facebook currently has a user base of more than 120 million members. According to the Facebook spokesman, very small percentage of users had been affected by these viruses.

The Koobface virus infects computers by sending notes to friends of someone whose computer has already been infected. The messages, with subject lines such as “You look just awesome in this new movie,” direct recipients to a website where they are requested to download a supposed update of Adobe Systems’ Flash player. Once  they download the software, users end up with an infected system, which then takes users to contaminated sites when they try to use search engines from Google, Yahoo, MSN, according to security experts. Numerous versions of the virus have been around since August.