Snort mailing list archives
RE: Snort+flexresp
From: "Sheahan, Paul (PCLN-NW)" <Paul.Sheahan () priceline com>
Date: Fri, 29 Mar 2002 13:25:57 -0500
You can never be sure if you are using all uppercase or lowercase. For example, I created a rule to alert and rst_all whenever a certain string is entered on a web page. Then to test, I went to the web page and entered the string. The rule was not triggered. When I went back to look at the trace to find out why it was not triggered, I found that even though I entered the string in lowercase on the webpage, the traces showed the string as all uppercase. I'm not sure why since I entered it in all lowercase. So changing my rule to use nocase, I no longer had to worry about that problem again. You just never know if the application you are using is going to change case on you behind the scenes! -----Original Message----- From: Onie Camara To: Sheahan, Paul (PCLN-NW) Cc: snort-users () lists sourceforge net Sent: 3/28/02 11:48 PM Subject: Re: [Snort-users] Snort+flexresp Ok. I do understand your point. But again, I am still on the testing stage. I am the only one that does ftp testing. And I know if I am using uppercase or lowercase. In this case, I am 100% sure that I am using a lowercase "anonymous" string. In the future, I will use nocase. :-) ----- Original Message ----- From: "Sheahan, Paul (PCLN-NW)" <Paul.Sheahan () priceline com> To: "'Onie Camara '" <neil () restricted dyndns org>; "Sheahan, Paul (PCLN-NW)" <Paul.Sheahan () priceline com>; "''Bamm Visscher' '" <bamm () satx rr com> Cc: <snort-users () lists sourceforge net> Sent: Thursday, March 28, 2002 10:44 PM Subject: RE: [Snort-users] Snort+flexresp
What I meant is, if you look at your rule below, you are looking for
the
content of "anonymous", but you don't have the nocase keyword entered
in
your rule. So if your FTP client had "anonymous" appear as "Anonymous"
or
"ANONYMOUS", then your rule would fail. In other words, I always try
and use
the nocase option, especially when a rule is not working as I expect,
but
nocase makes it fool-proof and helps me rule out the content as being
the
problem.... -----Original Message----- From: Onie Camara To: Sheahan, Paul (PCLN-NW); 'Bamm Visscher' Cc: snort-users () lists sourceforge net Sent: 3/28/02 8:27 PM Subject: Re: [Snort-users] Snort+flexresp Hi Paul, Are you talking about the string "anonymous" and snort's case sensitivity? If so, I wasn't using the anonymous string in uppercase. I am very
sure
of that. Or I misunderstood your post? Thanks. ----- Original Message ----- From: "Sheahan, Paul (PCLN-NW)" <Paul.Sheahan () priceline com> To: "'Bamm Visscher'" <bamm () satx rr com>; "Onie Camara" <neil () restricted dyndns org> Cc: <snort-users () lists sourceforge net> Sent: Thursday, March 28, 2002 7:13 PM Subject: RE: [Snort-users] Snort+flexrespNeil, I would stick the "nocase" option in your rule in case "anonymous"appearsin upper or mixed case. That has solved a few similar problems forme....Paul Sheahan Manager of Information Security Priceline.com paul.sheahan () priceline com -----Original Message----- From: Bamm Visscher [mailto:bamm () satx rr com] Sent: Thursday, March 28, 2002 7:04 PM To: Onie Camara Cc: snort-users () lists sourceforge net Subject: Re: [Snort-users] Snort+flexresp Neil, Try logging all the packets associated with your session and look toseethat 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
mysession wasn't kill by my rule? What's wrong with my rule? I even tried it with flags: A+, stilldidn'twork. 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.
Mostof the time, the source of an HTTP connection sends five
packets.
Twofor establishing the session (syn then ack), and two to tear
down
thesession (fin/ack and ack). Plus one that contains the
GET/POST/etc
request (usually a push/ack). It is impossible for flex-resp tokillthis session before the dest gets the GET/POST/etc, and thus it
is
impossible to create a rule to prevent the server from
processing
theGET/POST/etc request. If for some reason, the GET/POST/etccontains somuch data that it is spread across multiple packets, then you
may
have aslim chance at killing the session before the dest processes therequest(may the network lag be with you). The dest is going to send as many packets as it takes to returnthe inforequested, but killing the connection at that time is almostpointlesssince the server has already processed the perps
request/command.
Atbest 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 IDSusingtcp-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 thisthread.So now, what can you suggest me so that flex-resp will besuccessfulonkilling 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_______________________________________________ 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 _______________________________________________ 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 Bamm Visscher (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 Bamm Visscher (Mar 27)
- Re: Snort+flexresp Onie Camara (Mar 28)
- Re: Snort+flexresp Onie Camara (Mar 28)