The number of new variants of Koobface, a social networking worm that installs a trojan on victim machines, has skyrocketed during the month of June. According to Kaspersky Lab, the number of Koobface strains rose from 324 at the end of May to nearly 1,000 by the end of June. The worm, which spreads to friends in the form of an invitation to view a video, affects mostly Facebook and MySpace users. Recipients are asked to install a bogus Adobe Flash Player update to view the purported video, but doing so actually installs the trojan, which then spams the same same invite to friends and can steal data or change DNS settings. — DK