Hackers have used spamming software to distribute thousands of copies of a new Trojan. Email filtering firm MessageLabs alone has intercepted more than 4,000 copies of the Demonize-T Trojan over the last 24 hours.

Demonize-T is a multi-stage Trojan that uses an object data exploit in Internet Explorer (patch here) to download and execute an encoded visual basic script from a website. The Trojan then creates an executable file which appears to download a malicious program from the same website as the original script. Early analysis suggests Demonize-T is similar to previous attacks where malicious code has been used to install key loggers and password stealers.

Spammers are increasingly using infected as a platform to distribute spam and this technique has come full circle with virus writers using spam to infect machines in the first place.

Alex Shipp, senior anti-virus technologist at MessageLabs, said hackers are increasingly adopting the tactics of spammers in their attempts to seize control of as many machines as possible. MessageLabs typically block four or five bulk mail batches of Trojans a day. Mostly less than 20 messages are involved so the new attack - with more than 4,000 messages blocked in the space of only 24 hours - is far more intense. MessageLabs detected Demonize-T proactively, using its Skeptic predictive heuristics technology.

"Some parts of these Trojans are new but some code is old. Using old code is a funny tactic for virus writers to use because you can almost guarantee malware will be caught," Shipp commented. ®

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