Microsoft issued a patch Wednesday for a critical vulnerability in most versions of Windows that gives attackers remote control of a user's machine though Internet Explorer. But if the results of a new survey are any guide, most users won't install it.
The bug is a buffer overflow in an HTML conversion library used by a number of Windows programs, including Internet Explorer, and by extension Outlook and Outlook Express. To exploit it, an attacker tricks a victim into visiting a specially-crafted malicious Web page, or -- a more likely approach -- sends an Outlook user an HTML-formatted e-mail with the attack code embedded within.
A Russian hacker called "Digital Scream" reported the hole over Bugtraq on June 22nd, and other security researchers subsequently analyzed the vulnerability and produced a proof-of-concept exploit. With no advance warning, it took Microsoft seventeen days to release a patch -- not a unreasonable amount of time given the complexity of the problem, says Marc Maiffret, a founder of California-based security vendor eEye. "Since it is a component that is shared, and is not just used within Internet Explorer, it's a lot harder to test that the patch works with everything."
But even with a patch available, many users will likely remain vulnerable for years to come. At least that's what's suggested in a survey released Wednesday by the Belgian security company ScanIT, which has been operating a popular online browser security checker since last February.
ScanIT's free browser security test does not yet check for the HTML conversion hole, but it identifies 27 other known browser vulnerabilities -- most of them in Internet Explorer. Results collected from over 100,000 visitors to the site show that 86% of them suffer from at least one of those vulnerabilities, and 45% are susceptible to "high risk" vulnerabilities that give attackers remote access to the victim machine. Internet users in China were the most vulnerable, with 65% at high risk; American users the least, at 36%.
"Hackers are increasingly entering through flaws in Internet browsers themselves," said ScanIT's managing director David Michaux in a statement. "Developers put out patches regularly but most users aren't installing them."
Because Outlook and Outlook Express use Internet Explorer to display HTML formatted e-mail, the HTML conversion bug could be used to launch a virus or a worm. Last month's successful Bugbear.B worm relied on an Outlook security hole that Microsoft had patched more than two years earlier.
Microsoft rates the HTML conversion hole "critical" in Windows 98, Windows Me, Windows NT 4.0, Windows 2000, and Windows XP. The bug is merely a "moderate" hole in Windows Server 2003, owing to a default security setting that prevents automatic execution.
The company released two other less-serious advisories Wednesday, patching a buffer overflow in Windows' implementation of SMB, and a local privilege escalation vulnerability in Windows 2000's accessibility features.
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