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Interesting netflow entry
From: Wil Schultz <wschultz () wilcomm net>
Date: Mon, 06 Feb 2006 13:15:06 -0800


After setting up netflow this morning I have a of recurring flow that seems bothersome to me. I have an internal host (10.X.X.99) that continually attempts to hit various external hosts (AA, BB, CC, etc...) on seemingly random ports but always sources port udp.1204. In about 2 hours this host has hit 155 different external hosts, some of them once or twice and some of them more than 10 times. Below is a sanitised 10 minute output.

11:41:37.031 0.000 UDP 10.XX.XX.99:1204 -> AA.AA.AA.AA:46299 (RoadRunner, VA US) 11:42:07.032 0.000 UDP 10.XX.XX.99:1204 -> BB.BB.BB.BB:15989 (Comcast, MI US) 11:42:37.096 0.000 UDP 10.XX.XX.99:1204 -> CC.CC.CC.CC:52566 (Comcast, IL US) 11:43:17.204 0.000 UDP 10.XX.XX.99:1204 -> DD.DD.DD.DD:47756 (Adelphia, CA US) 11:45:27.521 0.000 UDP 10.XX.XX.99:1204 -> EE.EE.EE.EE:20797 (Tokyo) 11:46:07.685 0.000 UDP 10.XX.XX.99:1204 -> FF.FF.FF.FF:21363 (Surrey UK) 11:48:47.991 0.000 UDP 10.XX.XX.99:1204 -> GG.GG.GG.GG:48324 (Israel)

Interestingly enough, I've checked to see if this seemingly random port was actually listening and each of the 15-20 hosts I've checked are all listening on their port, i.e. AA.AA.AA.AA has udp.46299 open while BB.BB.BB.BB has udp.15989 open. When a host was contacted multiple times the "random" dstport is always the same.

Anyone have any clue on to what could be going on here?

-Wil


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