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Microsoft Posts Terminal Server Security Patch

Microsoft Corp. has posted a patch for a security hole that allows attackers to take down Windows NT Server 4.0, Terminal Server Edition with a denial-of-service attack.

Microsoft announced availability of the patch Monday in a security bulletin. Security vendor Internet Security Systems Inc. (www.iss.net) discovered the vulnerability.

Because Terminal Server responds to requests for new sessions by initiating the resource-intensive process of starting the session before it authenticates that the requester is a legitimate user, attackers can flood the server with bogus requests.

Terminal Server does not limit the system resources that can be devoted to setting up new sessions, so such an attack can crash the system. New legitimate connections would be blocked, existing sessions would fail and data could be lost.

According to Microsoft, an attacker cannot use the vulnerability to take administrative control of the system.

The patch gets around the problem by causing Terminal Server to authenticate the requester before processing the request. -- Scott Bekker

About the Author

Scott Bekker is editor in chief of Redmond Channel Partner magazine.