Blocking SMTP connections

[Hugo_vd_Kooij]

Is there a way to set a trip guard on SMTP connections and start blocking a source IP address after N failures on the SMTP protocol? SAM blocking comes to mind here.

The issue is I have a mail server (Barracuda Email Security Gateway) that gets hammered on every now and again by some silly system that tries hundreds of relay attempts with credential guessing. The barracuda blocks them after a few attempts but my log on the box fills up rather fast this way. I was just curious if there is way to block this in R80.10 with one of the blades.

Or do I need to get some extra logic device that will correlate the syslog events of the Barracuda and fire up a SAM blocking action? (Do I have a business case for Splunk here 😉

[Timothy_Hall]

Check out the fw samp and sim_dos commands.  You can establish a quota in SecureXL that will throttle/limit these connections and essentially tarpit them.  Once the spammer realizes you are doing this, they will go out of their way to leave you alone since you are slowing down their flow of spam.

[Hugo_vd_Kooij]

My first  attempt is ... interresting:

[Expert@fw01:0]# fw samp add -a d -l r quota service tcp/25 new-con-rate 1 track source
Segmentation fault (core dumped)

(I allready had a core dump this morning. So I wasn't looking for another one 😉

[Timothy_Hall]

Hmm I'd say so.  Firewall version?  Shouldn't that be new-conn-rate and not new-con-rate?  Although a seg fault is not exactly an appropriate response an incorrect parameter...

--
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[Hugo_vd_Kooij]

After HFA 56 it does not perform any core dumps.

[Keith_Mcdonald]

What is the command to execute for 80.20 FW version, Gaia OS. 5200.   I also want to rate limit my smtp traffic. But some of these commands have changed in 80.20. 

Thanks!

[Keith_Mcdonald]

Here is the corrected syntax for smtp connections coming in. 

fw samp add -a d -l r quota service 25 source any new-conn-rate 1 track source flush true

 80.20 this works on. Please apply this to your gateways.  The flush true at the end will ensure the rule gets applied immediately.