Adobe, the makers of Flash and security firm Kaspersky have warned of worms, named Koobface.a and Koobface.b that are spreading using social network sites Myspace and Facebook. The worms spread by sending messages to friends of an already infected user, encouraging them to click links. If the links are followed they direct a user to a site that includes a video clip, which cannot be viewed until a supposed 'update' is applied. While suspicious sites have commonly been used to spread viruses, the problem with links from social networks is that users tend to trust links that their friends (or in this case the worm) sends to them. That means the likelyhood of the worms spreading is higher. As always, it pays to be wary of anything that looks untrustworthy, even if a link comes from a suposedly trusted source.