Hackers have spammed out multiple new variants of the Bagle Trojan to millions of email addresses this week.

The attacks came in two waves on Monday and Tuesday and forced many anti-virus firms to issue multiple signature updates over a greatly compressed period.

Like previous versions of Bagle, each new variant tries to turn off security software while turning compromised machines into zombie drones under the control of hackers. The malware also tries to download further code from the internet.

"This Trojan horse is being aggressively seeded by its creator, using spam technology, to distribute malicious code to as many vulnerable computers as possible, in the shortest amount of time," said Graham Cluley, senior technology consultant at anti-virus firm Sophos.

Standard precautions apply: corporates should consider blocking executables at the gateway and update anti-virus signature definition files to detect the virus. Home users should also update anti-virus tools and resist the temptation to open suspicious-looking emails. ®

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