Skype's Instant messaging client has once again been misused as a vector to spread malware.

The Pykse-A worm is spreading via Skype instant messages, posing as a chat message linking to a website featuring racy picture of a young, scantily-clad woman. Clicking on these messages does display pics of a model wearing black lingerie, but only after an attempt has been made to infect PCs using a Trojan downloader that installs other items of malware. Infected PCs spread the infection by sending a variety of short messages promoting soft-core smut to an infected user's online friends using the Skype API.

The plausibility of the attack is increased because infected messages likely come from a target's list of known contacts, though the abrupt dialogue it generates from infected machines might trigger a few alarm bells. The malware sets the infected Skype user's status to DND (Do Not Disturb), another factor that might cause doubts about the authenticity of the bogus messages.

"Once it's up and running, the Pykse worm attempts to connect to a number of remote websites, presumably in an attempt to generate advertising revenue for them by increasing their number of 'hits'," said Graham Cluley, senior technology consultant for Sophos.

The malware is far from the first to use Skype's instant messaging client to spread. None of these attacks have proved particularly successful in the past. Anti-virus researchers reckon there's nothing about Pykse that will make it any more prolific. Most security firms consequently rate Pykse as a low risk threat. ®