nanog mailing list archives
Re: Syn flooding attacks
From: "Perry E. Metzger" <perry () piermont com>
Date: Mon, 20 Oct 1997 16:34:35 -0400
Joe Shaw writes:
Don't most SYN flood programs just send a constant stream of SYNs to the specified machine/port? The one I have for testing does that. So, sequential requests would get around this, no matter how many SYNs you were looking for. I think the best protection against SYN flooding is in the Kernel level of the OS. If you see a massive amount of SYN request coming in on one port from one machine or many, then you start applying cookies for those connections and decrease the hold time before you start dropping the connections due to un-answered SYN-ACKs. Don't most operating systems now support this feature (Win95 excluded)?
The whole "cookie" idea pretty much sucks, IMHO. It doesn't work particularly well. On the other hand, compressing your TCP state for half open connections is pretty cheap, and has the nice side effect of making your machine a much more efficient high volume server. Perry
Current thread:
- Syn flooding attacks Paulo Maffei (Oct 20)
- Re: Syn flooding attacks Phil Howard (Oct 20)
- Re: Syn flooding attacks Jeffrey C. Ollie (Oct 20)
- Re: Syn flooding attacks Peter Evans (Oct 20)
- Re: Syn flooding attacks Kenneth E. Gray (Oct 21)
- <Possible follow-ups>
- Re: Syn flooding attacks Vern Paxson (Oct 20)
- Re: Syn flooding attacks Joe Shaw (Oct 20)
- Re: Syn flooding attacks Perry E. Metzger (Oct 20)
- Re: Syn flooding attacks Joe Shaw (Oct 20)
- Re: Syn flooding attacks Jim Shankland (Oct 20)
- Re: Syn flooding attacks Perry E. Metzger (Oct 20)
- Re: Syn flooding attacks Phil Howard (Oct 20)