A security company claims to have found 10 major security flaws in Microsoft's Windows XP Service Pack 2, bypassing many of the security measures the update puts into place.
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According to Finjan Software, an attacker could exploit the flaws to execute malicious code on a user's system by luring the user to a specially crafted web page. Finjan has made the exploit's full technical details available to Microsoft but refused to make them public until the software giant has developed patches.
However, Microsoft said its initial analysis of the flaws showed they may not be as serious as the security firm claimed. "Our early analysis indicates that Finjan's claims are potentially misleading and possibly erroneous regarding the breadth and severity of the alleged vulnerabilities in Windows XP SP2," said a Microsoft spokesperson. "Microsoft encourages Finjan to abide by the principles of responsible disclosure and to decline to provide further comment or details on the alleged vulnerabilities until Microsoft is able to complete its investigation."
Finjan, which sells security software that it claims would plug the holes, had said the flaws allowed a web page to access a local file, elevating the privileges of code downloaded from the internet and bypassing SP2's system for alerting users to the download and execution of program files.
"By exploiting all vulnerabilities discovered in SP2 by Finjan, attackers can silently and remotely take over an SP2 machine when the user simply browses a web page," said Finjan.
Finjan stands by its claims. "We would not publish this kind of information unless we were 100% sure," said northern Europe sales manager Tim Warner. He said Finjan's standard procedure was to provide Microsoft with demonstrations for each vulnerability, showing how they could be easily exploited.
However, since no technical details have been made available, it is impossible to confirm the company's findings. The conflicting interests of the two parties are all too apparent: Finjan stands to gain publicity from discovering large holes in Microsoft's heavily hyped security update, whereas Microsoft will seek to downplay any holes until it has patches to fix them. Neither is likely to make the details public.
Warner defended Finjan's decision to publicise the existence of the SP2 bugs before a patch was available, saying they were so significant that users needed to be aware of them without delay. "There are some people out there who are thinking 'I've got SP2, therefore I'm safe.' The point here is that it's not safe. Vulnerabilities will always continue to come out - that's the nature of the game."
Microsoft said any patches would depend on the severity of the flaws. "If Microsoft finds any valid vulnerability in Windows XP SP2, it will take immediate and appropriate action, which may include releasing a fix out of band if such action is needed to protect customers."
Danish security firm Secunia criticised Finjan for taking the unorthodox step of publicising flaws while they were still being analysed by Microsoft. "I see no reason to go out and announce information about flaws in this manner," said Secunia chief technology officer Thomas Kristensen.
If researchers wanted to push IT companies into issuing patches more promptly, there were other ways to go about it, he said. He cited eEye Digital Security's Upcoming Advisories listing, which gives suppliers a push without providing potential attackers with clues.
Finjan's bugs, should they prove serious, would not be the first to be found in SP2. Shortly after SP2's release, a researcher publicised a bug that could allow a malicious website to plant executable code or script on a user's PC. Microsoft has patched one variant of this but another, publicised last month, is as yet unpatched. The unpatched variant also allows cross-site scripting.
Users can mitigate the problem by disabling the "Drag and drop or copy and paste files" option in Internet Explorer, disabling active content and setting the "Internet" zone to high security.
Kristensen said that while SP2 fixed many of Windows' underlying security vulnerabilities, Microsoft could have gone further. "It would probably break some functionality, but I think that would be perfectly acceptable considering the number of highly critical vulnerabilities pre-SP2."
He said it was just a matter of time before more SP2 flaws were found, as researchers and hackers gained a better understanding of how the new technology worked. "One serious hole has already been discovered and publicly disclosed. I'm certain we will see more in the near future," he said.
Matthew Broersma writes for Techworld