Not sure why Microsoft took time to acknowledge this?
"Microsoft has issued a security advisory to acknowledge a crippling
denial-of-service flaw affecting its newest operating systems — Windows
7 and Windows Server 2008 R2.
In the absence of a patch, Microsoft recommends that affected users
block TCP ports 139 and 445 at the firewall. Windows users should also
block all SMB communications to and from the Internet to help prevent
Microsoft confirms Windows 7 and Windows 2008 security hole