On Wed, 18 Sep 1996, Vern Paxson wrote:
have something in their logs like SYN/ACK RATIO 33:1 POSSIBLE HACKER ATTACK which will make them sit up and take notice.
I don't see how in reality to make the syn/syn-ack/ack ratio work soundly. It seems too easy for the cracker to synthesize bogus syn-ack's or ack's to manipulate the ratio however they please.
Wouldn't the ratio be calculated from outgoing SYN's and incoming ACK's? I can see that a sophisticated attacker could have a machine on another network sending incoming ACK's to balance the outgoing SYN's but I suspect this would be an extremely small percentage of attacks. Michael Dillon - ISP & Internet Consulting Memra Software Inc. - Fax: +1-604-546-3049 http://www.memra.com - E-mail: michael@memra.com