Forefront TMG detected a possible SYN attack and will protect the network accordingly

Question

Hi ,  Some times here internet is not working for using through TMG 2010. but Local Host Internet is working. then it should restart the 
Microsoft Forefront TMG Control with related Services. then again users can access the Internet  through TMG.
I check the Event Viewer in Server. it shows below Error Log.
Forefront TMG detected a possible SYN attack and will protect the network accordingly
what should for this ?
Regards, COMDINI

Answer 1

Hello,
An offending host attempts to flood Forefront TMG with half-open TCP connections by sending numerous TCP SYN messages to a Forefront TMG server and not completing the TCP handshake, leaving the TCP connections half-open.
Please enable logging to identified this hosts and then check if it is infected by viruses or malware programs.
Please see the value of the number of Maximum half-open TCP connections in Flood Mitigation settings for more information.
Once your problem is solved, you have to see "Forefront TMG is no longer experiencing a SYN attack." message.
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