Snort mailing list archives
Re: 1337 Bot and TCP options detection
From: Y M <snort () outlook com>
Date: Wed, 28 Dec 2016 16:43:57 +0000
You can use dsize as the following syntax and just have one rule. dsize:min<>max; http://manual-snort-org.s3-website-us-east-1.amazonaws.com/node33.html#SECTION00467000000000000000 YM On Wed, Dec 28, 2016 at 7:29 PM +0300, "joshua burgess" <avonyxx () hotmail com<mailto:avonyxx () hotmail com>> wrote: Unfortunately setting the Flowbits isn't an option because I'm using McAfee NSM and their half baked interpretation of SNORT which doesn't support it. As for my second rule can I create two different dsize variables to narrow the match down to inbetween two different packet sizes? Sent from Outlook<http://aka.ms/weboutlook> ________________________________ From: FOULDE Damien <damien.foulde () axians com> Sent: Wednesday, December 28, 2016 11:01:15 AM To: joshua burgess Cc: snort-sigs () lists sourceforge net Subject: RE: 1337 Bot and TCP options detection Joshua, To be able to match on the |01 03 03 07| content in the TCP header and then use the “flags” keyword you could split the rule and set a flowbit (http://blog.snort.org/2011/05/resolving-flowbit-dependancies.html) in a first snort ip rule and check this flowbit in a second snort tcp rule. Regards, Damien De : FOULDE Damien Envoyé : mercredi 28 décembre 2016 15:23 À : 'joshua burgess' Cc : snort-sigs () lists sourceforge net Objet : RE: 1337 Bot and TCP options detection Hello Joshua, You may write an ip rule, not a tcp one, to be able to match on the |01 03 03 07| content in the TCP header. However writing the snort rule through this way will prevent you to use the “flags” keyword reserved for the tcp rules. Regards, Damien De : joshua burgess [mailto:avonyxx () hotmail com] Envoyé : mercredi 28 décembre 2016 13:51 À : snort-sigs () lists sourceforge net<mailto:snort-sigs () lists sourceforge net> Objet : [Snort-sigs] 1337 Bot and TCP options detection To check a few boxes, I'm trying to gen up two signatures designed to detect the latest 1337 bot that Imperva wrote about (https://www.incapsula.com/blog/650gbps-ddos-attack-leet-botnet.html) Basically I'm trying to write a signature designed to detect the TCP options which spell out 1337 as well as an abnormally large SYN packet ranging from 799 to 936. I don't know SNORT supports my specifying the TCP options like: Number: No-Operation (NOP) (1) Kind: Window Scale (3) Length: (3) Shift count: (7) Could I do it with"content" only, it doesn't seem likely but I'm running out of ideas... alert tcp $EXTERNAL_NET any -> $HOME_NET any (msg:"1337 DDoS Tool"; flags:S; content:"Number: No-Operation (NOP) (1)"; content:"Kind: Window Scale (3)"; content:"Length: (3)"; content:"Shift count: (7)"; reference:url,https://www.incapsula.com/blog/650gbps-ddos-attack-leet-botnet.html; classtype:attempted-dos; sid:6000049; rev:1;) As far as writing a signature to look for just the SYN packet size would this work to set two different sizes? alert tcp $EXTERNAL_NET any -> $HOME_NET any (msg:"1337 DDoS Tool"; flags:S; dsize:>799; dsize:<936; reference:url,https://www.incapsula.com/blog/650gbps-ddos-attack-leet-botnet.html; classtype:attempted-dos; sid:6000049; rev:1;) Any help would be awesome. Thanks! Sent from Outlook<http://aka.ms/weboutlook>
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Current thread:
- 1337 Bot and TCP options detection joshua burgess (Dec 28)
- Re: 1337 Bot and TCP options detection FOULDE Damien (Dec 28)
- Re: 1337 Bot and TCP options detection FOULDE Damien (Dec 28)
- Re: 1337 Bot and TCP options detection joshua burgess (Dec 28)
- Re: 1337 Bot and TCP options detection Y M (Dec 28)
- Re: 1337 Bot and TCP options detection joshua burgess (Dec 28)