Microsoft Releases Patch to Improve TCP Initial Sequence Number Randomness
- By Scott Bekker
- October 25, 1999
Microsoft has released a patch that significantly improves the randomness of the TCP initial sequence numbers (ISNs) generated by the TCP/IP stack in Windows NT 4.0. Improving the randomness of ISNs eliminates a class of potential attacks against Windows NT 4.0 systems.
The ISNs used in TCP/IP sessions should be as random as possible in order to prevent attacks such as IP address spoofing and session hijacking. The patch offered by Microsoft improves the randomness of the Windows NT 4.0 TCP/IP ISN generation, providing 15 bits of entropy.
The patch works with Windows NT 4.0 Workstation, Server, Server Enterprise Edition and Server Terminal Edition. The patch is available at for x86 versions at download.microsoft.com/download/winntsrv40/patch/4.0.1381.7014/nt4/en-us/q24385.exe or for Alpha versions at download.microsoft.com/download/winntsrv40/patch/4.0.1381.7014/alpha/en-us/q243835.exe.
Scott Bekker is editor in chief of Redmond Channel Partner magazine.