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