Security experts are warning of a Trojan horse that can automatically attach spam to emails, instant messages and bulletin board postings.

Symantec researcher Eric Chien said that the malware uses a Windows layered service provider component to watch network traffic and alter outgoing messages and posts.

"Message board spam is nothing new," Chien explained on the company's security response blog. "But what is different about this message board spam is that the spam text is integrated into legitimate messages posted by real users. "

The attack begins when a user follows a link posted on a spam message or posting promising a 'funny video'. The user is then tricked into downloading an executable that installs the Trojan, formally known as Trojan.Mespam.

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