According to postings on the Internet security mailing list Bugtraq and Easynews Web portal, the infected Jpeg file was posted Monday. Users who download the file could allow attackers to take complete control of their systems.
Internet security information group Internet Storm Center issued an advisory saying the malicious file appears to have been developed using one of the many published "exploit kits" that are designed to make it easier to attack the MS04-028 vulnerability.
The center tested the attack-image file on unpatched Windows 2000 and XP SP1 systems running Internet Explorer. It said that while the malicious file managed only to crash Internet Explorer, better attacks are likely on the way. "We suspect that a working exploit is very close to widespread availability," wrote the center's Joshua Wright in the advisory.
Most popular antivirus apps can detect and protect against this attack, and Microsoft is urging users to update their systems with the patch included in its MS04-028 security bulletin.
See all the latest Microsoft security bulletins.