The Mega-D bot was shut down last year by FireEye network security after identifying it as a mega-source of spam.

ENGADGET: FBI charges 23-year old Russian in Mega-D spambot investigation

Although there have been malicious bots around for some time instant messaging, security firm IMLogic believes that this is the first time someone has tried to use bot code to help spread a worm around an IM network by pretending to be a legitimate user.

BBC: Hand on keyboard

Unlike a typical bot-net, which hijacks PCs with malicious software, that network of unwitting proxies wouldn't leave anything behind on victims' machines, making the attack harder to trace.

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