Microsoft has issued four security bulletins that patched just four vulnerabilities in Windows, Visual Studio and the MSN and Windows Live Messenger software, setting a 2007 record for the fewest flaws fixed in a monthly scheduled update.
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 Inc. "It's only rated 'important', but it patches a known vulnerability that's been publicly known for a week."
Messenger's Web cam 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 Web cam or video chat invitation risked losing control of their PC to the attacker, who could hijack the system by injecting and running his or her own code.
"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] Web cam session."
Rather than rely on users to open infected attachments -- a practice many users now know is dangerous -- new media attackers 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. "The most critical is the Microsoft Agent vulnerability," said Tom Cross, of IBM Internet Security Systems's X-Force, noting that the vulnerability could be exploited by well-known methods.
To exploit the vulnerability, an attacker would need to entice users to a malicious Web site. "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 near-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.
Cross also put the Agent patch at the top because Microsoft had credited three researchers 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 said.
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 posed a major threat.
Cross said that the Visual Studio bug first came to light in January and hadn't been exploited since.
Any threat to SFU was 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 five updates, but yanked one slated for SharePoint Services last Friday. Microsoft wouldn't say why it pulled the patch.
But talking up a fix and then not following through wasn't ideal, said analysts. "I wish they hadn't 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."
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).