[Snort-sigs] I need a rule for synk4.c attack

Ali BASEL alib at ...505...
Wed Apr 10 06:42:18 EDT 2002


How can I write a snort (snort 1.8.6) rule for the synk4.c syn flood 
(with spoofed IP) attack program ?

Here is the tcpdump of the attack:(destination port 80 supplied as an 
cat TCP\:1368-80
04/09-17:05:43.860348 ->
TCP TTL:30 TOS:0x0 ID:29579 IpLen:20 DgmLen:40
1*****S* Seq: 0x28376839  Ack: 0x0  Win: 0xFFFF  TcpLen: 20

I have tried the above rule to detect the attack, but It doesn't 
recognize it (I have changed the sequence number of the original rule)

alert tcp $HOME_NET any <> $EXTERNAL_NET any (msg:"DDOS shaft synflood"; 
flags: S; seq: 674719801; reference:arachnids,253; 
classtype:attempted-dos; sid:241; rev:2;)



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