Windows vulnerability can compromise credentials

A researcher with security vendor Cylance, Brian Wallace, found a new way to exploit a flaw originally found in 1997. Wallace wrote on Monday the flaw affects any PC, tablet or server running Windows and could compromise as many as 31 software programs.

He wrote the flaw was not resolved long ago, but that "we hope that our research will compel Microsoft to reconsider the vulnerabilities."

The vulnerability, called Redirect to SMB, can be exploited if an attacker can intercept communications with a Web server using a man-in-the-middle attack.

Windows or a program running on Windows can then be directed to communicate with a malicious SMB (server message block) server, which can then force an application to divulge the username, domain and hashed password of the person logged in, Wallace wrote.

Cylance disclosed its findings on Feb. 27 to the Computer Emergency Readiness Team at Carnegie Melon University, which issued an advisory.

CERT wrote that although the collected credentials are encrypted, attackers could try brute-force techniques -- which involves trying to guess a password -- until access is gained.

There are some mitigations. An attacker needs to be on the same network as a victim. It is also possible to block an attack by stopping outbound traffic on TCP ports 139 and 445, Wallace wrote.

Microsoft could not be immediately reached for comment.

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