'Critical' IE bug threatens PC users

A dangerous new exploit in Internet Explorer could put PCs and data at risk, Microsoft has admitted.

The flaw, for which code has already been published on the internet, could be exploited to set an email-borne virus free on the unsuspecting public.

Potential viruses could come as an attachment that conceals the code, or could possibly redirect users to a site that will unleash the code on the user's machine, leaving the computer open to remote attack. Once the PC is being controlled by a malicious user, it can then be used to launch attacks on other PCs.

Even supposedly fully patched versions of Internet Explorer 6 are vulnerable to the flaw, it seems, as are users with XP Service Pack 2.

However, Microsoft has no plans to patch it until its next security update is released. This is despite some security companies rating it as a high level threat.

In a security advisory on its website, Microsoft outlined the threat: "We have seen examples of proof of concept code but we are not aware of attacks that try to use the reported vulnerabilities or of customer impact at this time.

"Microsoft has determined that an attacker who exploits this vulnerability would have no way to force users to visit a malicious website."

Instead, it has warned users of its browser products to be careful when opening email attachments and to avoid untrusted websites. It has also recommended that users disable Active Scripting in their browser in an attempt to reduce their exposure to attack.

The other option is to choose an alternative browser, such as Firefox or Opera. However, even these browsers are not as safe from attack as they were once considered.

Firefox has been subject to a number of flaws over the past year, including one that could leave its users more vulnerable to phishing scams. Meanwhile, a report published in September by Symantec rated Internet Explorer as safer than Firefox. The report found some 25 flaws in Mozilla's Firefox internet browser, almost double the number it discovered in IE.

However, it has been a tough week for Microsoft - this is the third security flaw it has had to investigate in the past seven days. On Tuesday, it admitted it was looking into a security flaw that could leave Windows PCs open to remote control, while earlier in the week it also alerted users to a vulnerability that could cause the Internet Explorer browser to crash.

Copyright © 2006, ENN