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Cisco Security

TCP Segment Overwrite

 
Signature ID: 1300/0
Original Release:S149
Release:S637 (download)
Original Release Date:2005 March 04
Latest Release Date:2012 April 03
Default Enabled:True
Default Retired:False
Alarm Severity:High
Fidelity:85 

Description

This signature fires when one or more TCP segments in the same stream overwrite data from a one or more segments located earlier in the stream. This may indicate an attempt to hide an attack. Overwriting TCP segments do not normally occur and should be treated with suspicion.This signature will function in both promiscuous and in-line modes.

Recommended Filter

No recommended filters.

Benign Triggers

This signature may trigger upon analyzing traffic assigned to the same virtual sensor when the sensor is configured to monitor 2 or more networks, and the tcp connection is crossing 2 or more networks. If the sensor sees the same traffic twice within the same virtual sensor, this signature may fire. This signature may fire on traffic seen twice within the same virtual sensor when such traffic crosses multiple networks where an intermediate device may modify the packets (for example: a firewall or proxy server) Prior to version 6.0(1), the signature may fire on dual processor systems (running in dual thread mode) when there are no segment overwrites seen in network traffic. This is documented in Cisco defect ID CSCsg23774.

IntelliShield Alerts

IntelliShield ID Headline VersionCVSS ScoreLast Published
1160TCP Segment Manipulation22008 October 28 14:03 GMT
14071Cisco Content Switching Module TCP Packet Handling Denial of Service Vulnerability17.8/6.42007 September 05 16:29 GMT

Download

To download this and other IPS update files, please go to Cisco Secure Software Download.

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