there are few exist , you can use one of them according to your needs::
The open source log management tools are:
OSSEC (ossec.net) : an open source tool for analysis of real-time log data from Unix systems, Windows servers and network devices.
there may be other tools also exist ..
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Some time ago, the answer would be "Cisco MARS" ... ;-) Now I would recommend to look at Splunk: http://www.splunk.com
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