Week ago the UK group “Computer Terrorism” released a proof of concept exploit against patched versions of Internet Explorer. Microsoft is investigating this report of a vulnerability in Microsoft Internet Explorer on Microsoft Windows 98, on Windows 98 Second Edition, on Windows Millennium Edition, on Windows 2000 Service Pack 4, on Windows XP Service Pack 1, and on Windows XP Service Pack 2. Who are running Windows Server 2003 and Windows Server 2003 Service Pack 1 in their default configurations, with the Enhanced Security Configuration turned on, are not affected. Microsoft have also been made aware of proof of concept code and malicious software targeting the reported vulnerability.
You can visit Windows Live Safety Center and are encouraged to use the Complete Scan option to check for and remove this malicious software and future variants.