Denial of Service in Applications Using RPC over Named Pipes

Your Windows NT computer's responsiveness appears sluggish, and network clients may report a gradual decrease in system performance because of a Windows NT system process consuming 100 percent of CPU time. In addition, system memory usage may continually increase (potentially indicating a memory leak of system resources) up to the limit of available memory. The computer may stop responding (hang).

This problem is caused by a malicious attack on the remote procedure call (RPC) components in Windows NT using named pipes transport. Specific instances of this denial of service attack may be targeted at either the Spoolss.exe file or Lsass.exe file. There are different variations of the attack and each may create multiple named pipe connections to a Windows NT system and send random data. The RPC service then attempts to send a response and close each connection. The RPC service then cycles into a 100 percent CPU usage loop closing the invalid connections.

Windows NT Server and Workstation, Windows NT Server, Enterprise Edition

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the individual software update. For information on obtaining the latest service pack, please go to:

• http://www.microsoft.com/downloads/details.aspx?familyid=E396D059-E402-46EF-B095-A74399E25737&displaylang=en/ (http://www.microsoft.com/Windows/ServicePacks/) -or-
  
  
• 152734  (http://support.microsoft.com/kb/152734/EN-US/ ) how to obtain the latest windows nt 4.0 service pack

For information on obtaining the individual software update, contact Microsoft Product Support Services. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

Windows NT Server 4.0, Terminal Server Edition

To resolve this problem, obtain the latest service pack for Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

Windows NT Server and Workstation, Windows NT Server, Enterprise Edition

Microsoft has confirmed this problem could result in some degree of security vulnerability in Windows NT version 4.0. This problem was first corrected in Windows NT version 4.0 Service Pack 5.

Windows NT Server 4.0, Terminal Server Edition

Microsoft has confirmed this problem could result in some degree of security vulnerability in Windows NT version 4.0, Terminal Server Edition. Microsoft has confirmed that this is a problem in Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT Server 4.0, Terminal Server Edition Service Pack 4.

Using Windows NT Performance Monitor, you observe that, over time, the computer's CPU usage increases to 100 percent and remains there.