DOCUMENT:Q165005

TITLE   :Windows NT Slows Down Due to Land Attack

PRODUCT :Microsoft Windows NT

PROD/VER:4.00

OPER/SYS:WINDOWS

KEYWORDS:kbbug kbbug4.00 kbenv kbfix4.00 kbpatch NTSrvWkst nttcp



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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

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SYMPTOMS

========



After receiving spoofed connection request (SYN) packets, Windows NT may

begin to operate slowly. After about one minute, Windows NT returns to

normal operation.



NOTE: This problem may occur with TCP/IP on other operating systems as

well.



CAUSE

=====



This behavior occurs due to "Land Attack". Land Attack sends SYN packets

with the same source and destination IP addresses and the same source and

destination ports to a host computer. This makes it appear as if the host

computer sent the packet to itself. Windows NT operates more slowly while

the host computer tries to respond to itself.



RESOLUTION

==========



To resolve this problem, obtain the following fix or wait for the next

Windows NT service pack.



This fix should have the following time stamp:



   11/25/97  04:54p        143,472 Tcpip.sys (Intel)

   11/25/97  04:52p        263,375 Tcpip.sys (Alpha)



This hotfix has been posted to the following Internet location:



   ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/NT40/

   hotfixes-postSP3/land-fix/



NOTE: This fix supercedes the ICMP-fix and the OOB-fix hotfixes.



STATUS

======



Microsoft has confirmed this to be a problem in Windows NT version 4.0.

A supported fix is now available, but has not been fully regression-tested

and should be applied only to systems experiencing this specific problem.

Unless you are severely impacted by this specific problem, Microsoft

recommends that you wait for the next Service Pack that contains this fix.

Contact Microsoft Technical Support for more information.



MORE INFORMATION

================



For information on the hotfix for Windows 95, please see the following

article in the Microsoft Knowledge Base:



   ARTICLE-ID: Q177539

   TITLE     : Windows 95 Stops Responding Because of Land Attack



Additional query words: 4.00 port 139



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