By Gregg Keizer Framingham | Monday, 16 November, 2009
Microsoft late has confirmed that an unpatched vulnerability exists in Windows 7, but is downplaying the problem, saying most users would be protected from attack by blocking two ports at the firewall.
In a security advisory, Microsoft acknowledged that a bug in SMB (Server Message Block), a Microsoft-made network file- and print-sharing protocol, could be used by attackers to cripple Windows 7 and Windows Server 2008 R2 machines.
The zero-day vulnerability was first reported by Canadian researcher Laurent Gaffie last Wednesday, when he revealed the bug and posted proof-of-concept attack code to the Full Disclosure security mailing list and his blog. According to Gaffie, exploiting the flaw crashes Windows 7 and Server 2008 R2 systems so thoroughly that the only recourse is to manually power off the computers.
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Microsoft said it may patch the problem, but didn't spell out a timetable or commit to an out-of-cycle update before the next regularly-scheduled Patch Tuesday of December 8. Instead,
the company suggested users block TCP ports 139 and 445 at the firewall. Doing so, however, would disable a host of critical services, including network file-sharing and IT group policies.
http://computerworld.co.nz/news.nsf/scrt/E9592E1A9719742ACC25766F0066B38DAs a Slashdot wonk observed, this block needs to be on *outgoing* traffic, not incoming.