Microsoft issued a critical security warning Tuesday 16 December 2008 that a malicious exploit is attacking vulnerabilities in Internet Explorer 7.

The risk is believed to be widespread, given that IE 7 is the latest version of Microsoft's browser and is bundled with XP service pack 3 and also Vista.

The AZN Trojan, which surfaced the first week of December has the potential of infecting a users system with a Trojan horse, or a "downloader" that can download other forms of malware onto a system.

Microsoft announced it will release a security patch Wednesday 17 December 2008 via its automatic update system to patch users computers.

Users can potentially get infected two ways; one is to visit a malicious Web site that already has the malware installed on the site or by visiting a legitimate site in which an attacker has inserted the malicious script to run in the background, leaving visitors unaware their systems have been compromised.

A lot of Web sites are pushing out this exploit. Some of the infected sites include sites that offer free wallpaper for mobile phones to sites that feature property and product-related sites.