Microsoft confirmed on Friday (13/11) the existence of a vulnerability in Windows 7 , but said that most users can protect themselves from attacks by blocking two ports on the firewall.

In a security bulletin , Microsoft said that a flaw in Server Message Block (SMB), a protocol made ​​by the company, can be used by hackers to attack machines running Windows 7 and Windows Server 2008 R2.

The vulnerability was disclosed by Canadian researcher Laurent Gaffie on Wednesday (11/11). According to Gaffie, exploiting the flaw could reach the point where the system only method of recovery is a manual shutdown of the computer .

Initially, Microsoft said it would investigate the case, but on Friday confirmed the problem. "Microsoft is aware of a code that can be exploited to undermine the functioning of the system," said the representative of the company's security group Dave Forstrom. "The company is not afraid of attacks exploiting the vulnerability at this time."

Forstrom, as Graffie, said the error can be exploited to disable a computer, but the vulnerability does not allow the installation of malicious code on Windows 7.

Both SMBv1 SMBv2 as containing the error. "Windows Vista, Server 2008, XP, Server 2003 and 2000 are not affected," says Forstrom.

Attacks may be directed to any browser, not just Internet Explorer, Microsoft warned. After taking the user to access malicious websites, attackers could crash the victim's computer problem with SMB packets.

Microsoft should release a fix the problem, but did not include in the package is scheduled for December 8 or throws an isolated correction. The company suggests that users block TCP ports 139 and 445 at the firewall. However, this may disable browsers as well as cause other critical issues.