nanog mailing list archives

Re: Fkiws with destination port 0 and TCP SYN flag set


From: "Roland Dobbins" <rdobbins () arbor net>
Date: Wed, 17 Jun 2015 11:07:58 +0200


On 17 Jun 2015, at 10:44, Maqbool Hashim wrote:

It was stated in that thread that netflow reports source/dest port 0 for non-initial fragments.

Fragmentation in this context only applies to UDP packets.

If the destination of a TCP SYN is being reported as 0 (what's the source port?), either it's a reporting artifact of some kind or in fact a SYN destined to TCP/0 (we see this with SYN-floods, sometimes, as well as with attacks attempting to bypass ACL/firewall rules and related to compromise).

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Roland Dobbins <rdobbins () arbor net>


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