Microsoft have confirmed a bug with Server Message Block in Windows 7 that could allow attackers to cripple the machine runing Windows 7 but also Windows Server 2008 R2 machines.

So far the only fix available is to block port TCP ports 139 and 445 on your firewall but there is a catch. Blocking port 139 & 445 will disable browsers as well as a host of critical services, including network file-sharing and IT group policies as posted on NetworkWorld.com

I previously posted some tips on using Windows 7 for the first time that will help with security but now you should probably start looking at Blocking port 139 & 445 on your firewall. Windows 7 comes with a firewall installed that can be used to block these ports.

Microsoft has not yet confirmed a patch for the issue.