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The information in this article applies to:
- Microsoft Windows 95
- Microsoft Windows 95 OEM Service Release versions 1, 2, 2.1
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SYMPTOMS
========
After receiving spoofed connection request (SYN) packets over TCP/IP, a
computer running Windows 95 may begin to operate slowly. After about one
minute, Windows returns to normal operation.
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 packets to itself. Windows 95 operates more slowly while
the host computer tries to respond to itself.
RESOLUTION
==========
Without WinSock 2.0 Update
--------------------------
This issue is resolved by the following updated file for Windows 95 and
Windows 95 OEM Service Release 2 (OSR2) without the WinSock 2.0 update
only:
Vtcp.386 version 4.00.956 (dated 11/26/97) and later
To install this update, follow these steps:
1. Download the Vtcpup11.exe file from the Microsoft Software library to
an empty folder on your hard disk..
2. In My Computer or Windows Explorer, double-click the Vtcpup11.exe file
you downloaded in step 1.
3. Follow the instructions on the screen.
The following file(s) are available for download from the Microsoft
Software Library:
~ Vtcpup11.exe
For more information about downloading files from the Microsoft Software
Library, please see the following article in the Microsoft Knowledge Base:
ARTICLE-ID: Q119591
TITLE : How to Obtain Microsoft Support Files from Online Services
The following files are installed by Vtcpup11.exe:
File name Version Date/Time Size Destination folder
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Vtcp.386 4.00.956 11/26/97 9:56a 47,413 Windows\System
With WinSock 2.0 Update
-----------------------
Microsoft has confirmed this to be a problem in the WinSock 2.0 update for
Windows 95. We are researching this problem and will post new information
here in the Microsoft Knowledge Base as it becomes available.
STATUS
======
Microsoft has confirmed this to be a problem in Microsoft Windows 95 and
OEM Service Release 2 (OSR2). An update to address this problem is now
available, but is not fully regression tested and should be applied only
to computers experiencing this specific problem. Unless you are severely
impacted by this specific problem, Microsoft does not recommend
implementing this update at this time. Contact Microsoft Technical Support
for more information.
MORE INFORMATION
================
For additional information about this issue as it applies to Microsoft
Windows NT, please see the following article in the Microsoft Knowledge
Base:
ARTICLE-ID: Q165005
TITLE : Windows NT Slows Down Due to Land Attack
For additional information about issues resolved by updates to this
component, please see the following articles in the Microsoft
Knowledge Base:
ARTICLE-ID: Q170791
TITLE : Windows 95 TCP Clients Run Out of Ports
ARTICLE-ID: Q168747
TITLE : Update to Windows 95 TCP/IP to Address Out-of-Band Issue
Additional query words: 95
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