Microsoft KB Archive/195733

= Denial of Service in Applications Using RPC over Named Pipes =

Article ID: 195733

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Server 4.0, Terminal Server Edition
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Server 4.0 Standard Edition
 * Microsoft Windows NT Server 4.0 Enterprise Edition
 * Microsoft BackOffice Small Business Server 4.0

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This article was previously published under Q195733



SYMPTOMS
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).



CAUSE
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/windows/servicepacks/ -or-


 * 152734 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:

http://support.microsoft.com/directory/overview.asp

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:

152734 How to Obtain the Latest Windows NT 4.0 Service Pack



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.



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

Additional query words: denial of service nprpcfix

Keywords: kbhotfixserver kbqfe kbbug kbfix KB195733

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