[Snort-sigs] Trouble in triggering the snort rule to detect FTP Brute Force attack

Nigel Houghton nhoughton at ...435...
Mon Apr 12 09:00:20 EDT 2010


On Mon, Apr 12, 2010 at 7:58 AM, Eoin Miller
<eoin.miller at ...3415...> wrote:
> Could be because you are going from your $HOME_NET -> $EXTERNAL_NET when you
> are testing and your rule is only setup to trigger on $EXTERNAL_NET ->
> $HOME_NET.
>
> -- Eoin
>
> On 4/12/2010 6:07 AM, manjushree ks wrote:
>
> Hi,
>
> This is Manju writing in to request any suggestions on the below snort rule,
>
> Rule that will detect more than 3 unsuccessful login attempts on a FTP
> server within a minute with username administrator or Administrator or
> ADMINISTRATOR. The Hacker is trying to login with the username administrator
> or Administrator orADMINISTRATOR.
>
>
> Below is the rule that I have been trying out,
>
> alert tcp $EXTERNAL_NET any -> $HOME_NET 21 (msg:"FTP Potential Brute Force
> Attack"; flow:to_server,established;content:"530
> ";depth:4;pcre:"/530\s+(Login|User|Failed|Not|Logged|In)/smi";content:"Administrator";
> nocase;threshold:type threshold, track by_src, count 3,seconds 60;
> classtype:suspicious-login; sid:3000002;)
>
> I have tried to login into a FTP server and below are the results,
>
> ******************************************
> root at ...3478...:~# ftp ftp.microsoft.com
> Connected to ftp.microsoft.akadns.net.
> 220 Microsoft FTP Service
> Name (ftp.microsoft.com:manjushree): administrator
> 331 Password required for administrator.
> Password:
> 530 User cannot log in.
> Login failed.
> Remote system type is Windows_NT.
> ftp> user administrator
> 331 Password required for administrator.
> Password:
> 530 User cannot log in.
> Login failed.
> ftp> user administrator
> 331 Password required for administrator.
> Password:
> 530 User cannot log in.
> Login failed.
> ************************************************
>
> But I dont have alerts being triggerd. Could anyone please let me know where
> am I going wrong?
>
> Thanks!
> Manju
>
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This looks suspiciously like a question from a student on a course
that includes Snort in it. i.e. A contrived situation.

The answers you seek are in the snort manual, the README files and the
many other sources of information on the Internet.

-- 
Nigel Houghton
Head Mentalist
SF VRT
http://vrt-sourcefire.blogspot.com && http://labs.snort.org/




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