Re: Rules to block FT

["Joel Ebrahimi" <jebrahimi () stillsecure com>]

Hi Dwane,

There is a problem with this rule. The content detection portion of the rule looks good, it looks for the 530 response 
from FTP for an incorrect login. 
The problem lies within the rule header though (alert tcp $HOME_NET any -> $EXTERNAL_NET 21), this content that is 
being looked for is from the client to the server, where it is really the server that sends the 530 error code so by 
switching the direction your monitoring this pattern for you should be good to go (alert tcp $EXTERNAL_NET 21 ->  
$HOME_NET any).

//Joel 

StillSecure
Joel Ebrahimi
Senior Software Engineer


http://www.stillsecure.com/
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-----Original Message-----
From: snort-users-bounces () lists sourceforge net on behalf of Atkins, Dwane P
Sent: Wed 6/27/2007 9:18 AM
To: Snort-users () lists sourceforge net
Subject: [Snort-users] Rules to block FT
 
I have a testbed set up and have already alerted and blocked via
snortsam for SSH.  I am now working on FTP.

 

My rule:

 

alert tcp $HOME_NET any -> $EXTERNAL_NET 21 (   msg:"BLOCKED Potential
FTP Brute-Force attempt";flow:from_server,established; content:"530 ";
pcre:"/^530\s+(Login|User|Failed)/smi";classtype:unsuccessful-user;
threshold: type threshold, track by_dst, count 10, seconds 60;
sid:1000002; rev:1; fwsam: src, 5 minutes;)

 

Does this look like it will work? I am not that adept about building
rules and am learning.  This was from bleeding edge, I think.

 

Dwane

 


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