Snort mailing list archives
Re: Snort+flexresp
From: "Onie Camara" <neil () restricted dyndns org>
Date: Thu, 28 Mar 2002 19:14:03 -0600
Hi Bamm, It worked when I modified resp:rst_all. I placed a space after resp: But flex-resp, from my testing, only sometimes kill my tcp session. alert tcp $HOME_NET any -> $EXTERNAL_NET 21 (msg:"FTP access from anonymous"; flags:!R ; resp: rst_all;content:"anonymous"; classtype:not-suspicious; sid:1717; rev:2;) So when i ftp to somewhere from the commandline, right after pressing Enter key on the anonymous entry on username, I get disconnected. I got impressed with that. But I tried it again, it allowed me to login. I tried both rst_all and rst_snd, same behavior. So looks like, flex-resp code is not ready for production. ----- Original Message ----- From: "Bamm Visscher" <bamm () satx rr com> To: "Onie Camara" <neil () restricted dyndns org> Cc: <snort-users () lists sourceforge net> Sent: Thursday, March 28, 2002 6:04 PM Subject: Re: [Snort-users] Snort+flexresp
Neil, Try logging all the packets associated with your session and look to see that there are RESETs being sent. It should work. Bammkkkk On Thu, 2002-03-28 at 09:50, Onie Camara wrote:Ok. I created a rule. alert tcp $HOME_NET any -> $EXTERNAL_NET 21 (msg:"FTP access from anonymous"; flags:!R ; resp:rst_all;content:"anonymous"; classtype:not-suspicious; sid:1717; rev:2;) And here is the log: [**] [1:1717:2] FTP access from anonymous [**] [Classification: Not Suspicious Traffic] [Priority: 3] 03/28-09:45:49.271952 192.168.0.112:1062 -> 129.128.5.191:21 TCP TTL:64 TOS:0x10 ID:60673 IpLen:20 DgmLen:68 DF ***AP*** Seq: 0xF518481 Ack: 0x678EB95E Win: 0x8218 TcpLen: 32 TCP Options (3) => NOP NOP TS: 11758512 213343883 You mentioned that flex-resp is friendly to ssh, ftp, .etc. How come my session wasn't kill by my rule? What's wrong with my rule? I even tried it with flags: A+, still didn't work. But I still admin that I am not good on those flags. Thank you. ----- Original Message ----- From: "Bamm Visscher" <bamm () satx rr com> To: "Ronneil Camara" <ronneilc () remingtonltd com> Cc: <snort-users () lists sourceforge net> Sent: Wednesday, March 27, 2002 7:06 AM Subject: RE: [Snort-users] Snort+flexrespNeil, There is no way to force flex-resp to be successful against HTTP. Most of the time, the source of an HTTP connection sends five packets. Two for establishing the session (syn then ack), and two to tear down the session (fin/ack and ack). Plus one that contains the GET/POST/etc request (usually a push/ack). It is impossible for flex-resp to kill this session before the dest gets the GET/POST/etc, and thus it is impossible to create a rule to prevent the server from processing the GET/POST/etc request. If for some reason, the GET/POST/etc contains so much data that it is spread across multiple packets, then you may have
a
slim chance at killing the session before the dest processes the
request
(may the network lag be with you). The dest is going to send as many packets as it takes to return the
info
requested, but killing the connection at that time is almost pointless since the server has already processed the perps request/command. At best you might prevent the perp from seeing all the results of a directory listing. BTW, this is not a snort specific problem. It affect every IDS using tcp-resets to kill connections. Bammkkkk On Wed, 2002-03-27 at 00:36, Ronneil Camara wrote:Hi Bamm, I got impressed on how you answered your every post on this thread. So now, what can you suggest me so that flex-resp will be successful
on
killing connections let say for http? Thank you very much. Neil_______________________________________________ Snort-users mailing list Snort-users () lists sourceforge net Go to this URL to change user options or unsubscribe: https://lists.sourceforge.net/lists/listinfo/snort-users Snort-users list archive: http://www.geocrawler.com/redir-sf.php3?list=snort-users
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Current thread:
- Re: Snort+flexresp, (continued)
- Re: Snort+flexresp Jeff Nathan (Mar 25)
- Re: Snort+flexresp Bamm Visscher (Mar 26)
- Re: Snort+flexresp Jeff Nathan (Mar 26)
- Re: Snort+flexresp Roelof JT Jonkman (Mar 13)
- Re: Snort+flexresp Jeff Nathan (Mar 27)
- Re: Snort+flexresp Onie Camara (Mar 28)
- Re: Snort+flexresp Bamm Visscher (Mar 28)
- Re: Snort+flexresp Onie Camara (Mar 28)
- Re: Snort+flexresp Bamm Visscher (Mar 28)
- Re: Snort+flexresp Onie Camara (Mar 28)
- Re: Snort+flexresp Onie Camara (Mar 28)
- Re: Snort+flexresp Onie Camara (Mar 28)