Microsoft Tuesday patched three vulnerabilities in the company's Server Message Block (SMB) file-sharing protocol, including two that could make "swiss cheese" out of enterprise networks, according to one researcher.
"This is super nasty," said Eric Schultze, the chief technology officer at Shavlik Technologies, who also called today's update "super critical" as he rang the alarm. "Expect to see a worm on this one in the very near future, [because] this is Blaster and Sasser all over again."
Those two worms, 2003's Blaster and 2004's Sasser, wreaked havoc worldwide as they spread to millions of Windows machines.
Of the three bugs outlined in the MS09-001 security bulletin, two were rated "critical," the most serious ranking in Microsoft's four-step scoring system, while the third was pegged "moderate."
The pair pegged as critical are extremely dangerous because attackers can exploit them simply by sending malformed data to unpatched machines, Schultze continued. "These flaws enable an attacker to send evil packets to a Microsoft computer and take any action they desire on that computer [with] no credentials required," he said. "The only pre-requisite for this attack to be successful is a connection from the attacker to the victim over the NetBIOS ports, TCP 139 or TCP 445. By default, most computers have these ports turned on."
Much the same situation led to Blaster and Sasser, Schultze noted. "More people have blocked those ports, and more personal firewalls block them by default, but they are typically left open in a corporate network."
Amol Sarwate, manager of Qualys' vulnerability lab, agreed. "The ports are always open [in the enterprise] and no user intervention is needed," he said. "This is nasty."
Today's update affects all currently-supported versions of Windows, including Windows 2000, XP, Server 2003, Vista and Server 2008, Microsoft noted, although the newer editions -- Vista and Server 2008 -- are immune from one of the two critical vulnerabilities. The second critical bug, also wormable from Schultze's and Sarwate's perspectives, is rated as moderate for Vista and Server 2008 because those two operating systems have file sharing disabled by default.
That, and other mitigating circumstances, must be why Microsoft gave the three bugs its lowest exploitability index rating, even though two carried critical severity rankings, said Andrew Storms, director of security operations at nCircle Network Security.
"This might be the first time that Microsoft has labeled a critical vulnerability all the way down to '3' on the exploitability index," said Storms, talking about Microsoft's relatively new practice of predicting the likelihood of attackers coming up with successful exploits in the coming month. Microsoft tagged all three of today's bugs with a "3" on its exploitability index. According to the company, a "3" means "functioning exploit code is unlikely."