DOCUMENT:Q195733  20-MAY-2002  [winnt]
TITLE   :Denial of Service in Applications Using RPC over Named Pipes
PRODUCT :Microsoft Windows NT
PROD/VER:WinNT:4.0
OPER/SYS:
KEYWORDS:kbWinNT400sp5fix _IK

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The information in this article applies to:

 - Microsoft Windows NT Workstation version 4.0 
 - Microsoft Windows NT Server version 4.0 
 - Microsoft Windows NT Server, Enterprise Edition version 4.0 
 - Microsoft Windows NT Server version 4.0, Terminal Server Edition 
 - Microsoft BackOffice Small Business Server version 4.0 
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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.


RESOLUTION
==========

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

 - Q152734 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/default.aspx?scid=fh;EN-US;CNTACTMS


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

   Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack


STATUS
======

Windows NT Server and Workstation, 
Windows NT Server, Enterprise Edition
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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
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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 this to be 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
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Keywords          : kbWinNT400sp5fix _IK 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400 kbWinNTS400search kbWinNTS400 kbNTTermServ400 kbNTTermServSearch kbAudDeveloper kbSBServSearch kbSBServ400
Version           : WinNT:4.0
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbfix

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PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND.  MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
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SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 2002.