Security experts have issued a low-key alert about a Trojan horse which exploits Microsoft's ActiveX applet programming language.

Called Offensive, The Trojan comes in the form of an HTML file or a Web page on the Internet. Offensive is potentially dangerous, but it appears difficult to become a victim.

An attacker would have to either send the Trojan directly to a user in an email (it has no worm-like characteristics), or construct a maliciously constructed Web page which few are likely to visit, in order to try and infect people.

One variant of the Trojan will activate as soon as an HTML file is opened, so users of Outlook or Outlook Express are advised to delete suspicious emails without opening them.

If activated, Offensive might modify a user's home page as well as to severely restrict your access to a system, including preventing you starting programs and frustrating attempts to shut down a system

Andre Post, senior researcher at Symantec, said that it would take a "lot of work undoing its effects".

All this sounds rather nasty but Symantec assure us the Trojan is low risk for a number of reasons.

Firstly Offensive has failed to spread widely and does not pose a particularly high risk because the default security settings of Internet Explorer should - by default - block it's execution.

Users with fully patched versions of IE 5.5 are also immune, whatever the security settings on their browser. More information on the Trojan is available on Symantec's Web site here. ®

External links

Write-up of Offensive Trojan by Symantec

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