Denial of Service in Applications Using RPC over Named Pipes

ID: Q195733

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

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

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/

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://www.microsoft.com/support/supportnet/overview/overview.asp

NOTE: If this product was already installed on your computer when you purchased it from the Original Equipment Manufacturer (OEM) and you need this fix, please call the Pay Per Incident number listed on the above Web site. If you contact Microsoft to obtain this fix, and if it is determined that you only require the fix you requested, no fee will be charged. However, if you request additional technical support, and if your no-charge technical support period has expired, or if you are not eligible for standard no-charge technical support, you may be charged a non-refundable fee.

For more information about eligibility for no-charge technical support, see the following article in the Microsoft Knowledge Base:

Q154871 Determining If You Are Eligible for No-Charge Technical Support

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, 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

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 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

Keywords : kbbug4.00 kbfix4.00 nt4sp5fix TSESP4Fix
Version : WinNT:4.0
Platform : winnt
Issue type : kbbug