Patch Tuesday was quieter than usual for Microsoft users this month, with the company issuing just four security bulletins yesterday.
Four vulnerabilities were fixed in Windows, Visual Studio and the MSN and Windows Live Messenger software, setting a 2007 record for the fewest flaws fixed in a month's scheduled updates.
Only one of the four flaws was pegged critical, Microsoft's highest threat warning, while the other three were all labelled important, a notch lower.
Two security analysts pointed at MS07-054, the update for Microsoft's instant messaging clients - MSN Messenger and the newest Windows Live Messenger - as the one to deploy first. "It's the most interesting," said Andrew Storms, director of security operations at nCircle Network Security. "It's only rated important, but it patches a known vulnerability that's been publicly known for a week."
Messenger's webcam vulnerability was first reported late last month on a Chinese-language security mailing list, and exploit code for the flaw has made its way onto the Internet. Users duped into accepting a malicious webcam or video chat invitation risked losing control of their PC to the attacker.
"This is the most important one," agreed Amol Sarwate, manager of Qualys' vulnerability lab. "It falls into this new trend of new media attacks using social engineering. By 'new media,' I mean exploits inside images, inside MP3 files and, in this case, inside [a] webcam session." Rather than rely on users to open infected attachments - a practice many users now know is dangerous - new media attacks hope that users' guards are down when they receive chat invitations via IM.
But one researcher fingered a different bulletin - MS07-051 - as the one to deploy pronto. "The most critical is the Microsoft Agent vulnerability," said Tom Cross, of IBM Internet Security Systems' X-Force, noting that the vulnerability could be exploited by well-known methods. To exploit it, an attacker would need to entice users to a malicious website. "It uses a pretty common attack vector," he said, "and fits the profile of a lot of bugs."
Microsoft Agent, said Cross, has been patched previously. An April update, in fact, fixed a nearly-identical flaw. Agent, the Windows component that makes possible the interactive animated help characters - the infamous "Clippy" once used in Microsoft Office is probably the best-known example - was patched in April on most versions of Windows. This month, the fix was in for Windows 2000 SP4 only.
Another factor that drove Cross to put the Agent patch at the top of this list was that three researchers were credited by Microsoft for reporting the bug. "So many people discovered this vulnerability more or less simultaneously that if it remains unpatched, people on the other side might discover it too," Cross reasoned.
The other two updates quashed bugs in Visual Studio and in the Windows Services for Unix (SFU), a collection of components that make it possible for Windows and Unix systems to talk to each other. Both updates were rated important by Microsoft, but the analysts said that neither flaw poses a major threat.
In fact, Cross said that the Visual Studio bug first came to light in January and hasn't been exploited in the intervening months.
And the threat to SFU is mitigated by the niche-like nature of the service. "Very few people use this," said nCircle's Storms. "Most use the Cygwin tools instead."
Microsoft originally planned to issue five updates, but yanked one slated for SharePoint Services last Friday. Microsoft declined to specify why it pulled the patch, but previously when it has culled a list of scheduled updates, it has made general statements about not releasing patches until their quality meets the company's expectations.
But talking up a fix and then not following through isn't ideal, said analysts. "I wish they wouldn't have said anything about SharePoint," said Cross.
Storms agreed. "There must be a reason why they pulled it, and it had to be a pretty good reason," he said. "But now we all know that there's a vulnerability in SharePoint."
This month's updates fixed just four flaws, and that's the lowest number of vulnerabilities in a month when Microsoft issued patches. The company also issued four bulletins in January, but they addressed 10 flaws. It posted no patches in March.
As usual, Microsoft's monthly updates are available via the Microsoft Update and Windows Update services, as well as through Windows Server Update Services (WSUS).