In addition to issuing three patches for potentially critical flaws in its Internet Explorer on Tuesday, Microsoft launched the Windows Malicious Software Removal Tool.

Microsoft rated two of the flaws in IE "critical" and a third "important" after the company discovered that malicious code could exploit holes in the browser.

The HTML Help vulnerability detailed in Security Bulletin MS05-001 could allow information disclosure or remote code execution on an affected system, according to the bulletin. An attacker could exploit the vulnerability by constructing a malicious Web page that could potentially allow remote code execution if a user visited that page. According to Microsoft, which gave it a critical rating, even when equipped with the latest Service Pack 2 (SP2) patch, end users were vulnerable to Trojan attacks.

Last month, Chinese security group xFocus reported the flaw before the patch cycle, which drew the ire of Microsoft. The company argued the action put computer users at risk.

Security Bulletin MS05-002 highlights vulnerabilities in cursor and icon format handling. This vulnerability, which Microsoft rated critical, could allow an attacker to try and exploit the vulnerability by constructing a malicious cursor or icon file that could potentially allow remote code execution if a user visited a malicious Web site or viewed a malicious e-mail message, according to the bulletin.

A Denial of Service (DoS) vulnerability is also highlighted in Security Bulletin MS05-002, and it affects the way that cursor, animated cursor and icon formats are handled. An attacker could try to exploit the vulnerability by constructing a malicious cursor or icon file that could potentially cause the operating system to become unresponsive, according to the bulletin.

The third vulnerability patched today exists in the Indexing Service because of the way that it handles query validation, according to Security Bulletin MS05-003 An attacker could exploit the vulnerability by constructing a malicious query that could potentially allow remote code execution on an affected system. An attack, according to the bulletin, would most likely result in a DoS condition.

The monthly patch cycle, which occurs the second Tuesday of every month, will now include updates of the anti-malicious software removal tool, according to a Microsoft spokeswoman.

The spokeswoman said the updates to the removal tool are an extension of virus or worm removal tools that Microsoft released in 2004.

The first version of the tool, available for for download, is capable of removing numerous viruses and worms, as well as their variants, including: Blaster, Sasser, MyDoom, DoomJuice, Zindos, Berweb, Gailbot and Nachi.

While tools released in 2004 have been specific to a single virus and some of its variants, the new removal tool targets numerous viruses.