[Snort-sigs] sid 2586 False positive documentation

Burtoft, Jim jburtoft at ...2813...
Mon Feb 21 07:05:16 EST 2005


Message:  P2P eDonkey transfer
 
False positives:  This rule triggers when there is any traffic that has a source port of 4242 and the first hex byte is E3.  In our shop, this seems to happen regularly (once or twice a week) in SSL communication sessions (destination port 443) that just happen to have been dynamically assigned a source port of 4242.
 
I am not sure is this is characteristic of our network, or just the fact that any encrypted communication has an approximately 1/256 chance of beginning with the byte E3 (assuming encrypted traffic emulates a random distribution).  Of course, it only triggers the alert when the source port happens to be 4242 (perhaps soon after the client reboots?).
 
Jim


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