DOCUMENT:Q177539 TITLE :Windows 95 Stops Responding Because of Land Attack PRODUCT :Microsoft Windows 95 PROD/VER:95 OPER/SYS:WINDOWS KEYWORDS:kbbug kbenv kbpatch --------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows 95 - Microsoft Windows 95 OEM Service Release versions 1, 2, 2.1 --------------------------------------------------------------------- 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 ---------------------------------------------------------------------- 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 ============================================================================ THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.