[Snort-users] Rules to block FT

Valter Santos vsantola at ...13607...
Thu Jun 28 13:20:07 EDT 2007


Hi all,

I think what Dwane is looking for is ftp brute force attempts against
his own ftp servers, so this should do it:

alert tcp $HOME_NET 21 -> $EXTERNAL_NET any

Responses from $HOME_NET 21 to external hosts... the full rule from
bleeding threats:

alert tcp $HOME_NET 21 -> $EXTERNAL_NET any (msg:"BLEEDING-EDGE SCAN
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 5, seconds 120; sid:2002383; rev:4;)


take care
/valter




On 6/28/07, Joel Ebrahimi <jebrahimi at ...13458...> wrote:
>
>
>
> 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 at lists.sourceforge.net on behalf
> of Atkins, Dwane P
>  Sent: Wed 6/27/2007 9:18 AM
>  To: Snort-users at 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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