On Mon, 16 Sep 1996, Craig A. Huegen wrote:
The SYN flood coming towards my host X looks like this, at approximately 2,000 PPS:
182.58.239.2.1526 -> 172.30.15.5.80 TCP SYN 19.23.212.4.10294 -> 172.30.15.5.80 TCP SYN 93.29.233.68.4355 -> 172.30.15.5.80 TCP SYN [... on and on ...]
Tell me how to filter this.
The only thing that comes close to the concept of "filtering" is to build a SYN proxy that replies with SYN-ACK and hangs onto SYN packets until the ACK is received from the net before actually letting the packets through to your server. This may require sequence number munging on every packet but that's generally the kind of thing proxies do. Of course, such a proxy does not yet exist except possibly as somebody's home-built box based on some stripped down BSD-ish UNIX kernel with various modifications. But assuming that you can build a box with enough horsepower to handle 100baseTx/FDDI/whatever in and 100baseTx/FDDI/whatever out, then this is in the realm of possibility. Michael Dillon - ISP & Internet Consulting Memra Software Inc. - Fax: +1-604-546-3049 http://www.memra.com - E-mail: michael@memra.com