lots of connections in SYN_RECV state

Silvan Jegen me at sillymon.ch
Thu Nov 6 09:30:46 EST 2014


Hi

Am 2014-11-06 14:27, schrieb Puneet Agarwal:
> I have a couple of servers, for the past few days I am seeing lots of
> connections in SYN_RECV state in netstat commands output.

This *could* be the result of a SYN-flood attack on your server.


> Is there a solution to this problem?

The Wikipedia page mentions some countermeasures (if it indeed is an 
attack and not a networking stack issue).

http://en.wikipedia.org/wiki/SYN_flood

Maybe you could check from which IP addresses these SYNs come from and 
investigate why they do not answer to the SYN-ACK request of your 
server.


Cheers,

Silvan



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