Microsoft Issues Internet Explorer Security Advisory

Users of Internet Explorer 6 and 7 may be vulnerable to a malware attack.

Thomas Claburn, Editor at Large, Enterprise Mobility

November 24, 2009

2 Min Read

The publication of proof-of-concept exploit code affecting Internet Explorer 6 and 7 over the weekend prompted Microsoft on Monday to issue a Security Advisory.

Microsoft says that it is investigating the reported vulnerability, which affects Internet Explorer 6 Service Pack 1 on Microsoft Windows 2000 Service Pack 4, and Internet Explorer 6 and Internet Explorer 7 on Windows XP, Windows Server 2003, Windows Vista, and Windows Server 2008.

Internet Explorer 5.01 Service Pack 4 and Internet Explorer 8 are not affected.

Microsoft says that it is not aware of attacks attempting to exploit the reported vulnerability.

"The vulnerability exists as an invalid pointer reference of Internet Explorer," Microsoft's Advisory states. "It is possible under certain conditions for a CSS/Style object to be accessed after the object is deleted. In a specially-crafted attack, Internet Explorer attempting to access a freed object can lead to running attacker-supplied code."

The fact that Internet Explorer 6 and 7 together account for about 41% of the Web browser market means attackers will be tempted to exploit the vulnerability, says Michael Sutton, VP of security research at Zscaler, a computer security company.

"Attacks such as these are also prime candidates for targeting otherwise legitimate Web sites as an attack vector," Sutton said in an e-mailed statement. "The exploit can be triggered simply via HTML code, so attackers can inject code into Web sites with weak security protections."

According to Symantec Security Response, the proof-of-concept exploit exhibits inconsistent behavior.

Symantec expects that future exploits prove more effective.

While Microsoft has yet to issue a patch for the vulnerability, its advisory offers several ways to mitigate the risk of attack.

Finding the flaws in your operating systems and applications is only the beginning. You then need to plot a path to security and ensure that no new weaknesses find their way onto your network. This Dark Reading report focuses on how to do that. Download the report here (registration required).

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About the Author(s)

Thomas Claburn

Editor at Large, Enterprise Mobility

Thomas Claburn has been writing about business and technology since 1996, for publications such as New Architect, PC Computing, InformationWeek, Salon, Wired, and Ziff Davis Smart Business. Before that, he worked in film and television, having earned a not particularly useful master's degree in film production. He wrote the original treatment for 3DO's Killing Time, a short story that appeared in On Spec, and the screenplay for an independent film called The Hanged Man, which he would later direct. He's the author of a science fiction novel, Reflecting Fires, and a sadly neglected blog, Lot 49. His iPhone game, Blocfall, is available through the iTunes App Store. His wife is a talented jazz singer; he does not sing, which is for the best.

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