Re: [Snort-users] Rules to block FT

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@stillsecure.com> 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@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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