Solved

Setting an SMTP connection / IP threshold in ASA and blocking non-complying traffic

Posted on 2006-10-25
7
320 Views
Last Modified: 2010-05-18
Hello
I have a 2620 XM connected to an ASA5510 firewall. the ASA has 3 interfaces, one for connecting to the 2620XM (for internet connection.) 1 for DMZ and 1 for the internal network.
I have a mail server behind the DMZ that has SMTP ports open to the public internet.
On some days, I get 150.000 + SMTP connections that are trying to send spam / relay through my server. My anti-spam settings on my mail server detect this and bounce the emails, but the sheer number of connection attempts etc. are a heav load on my server. Is there a way I can set up my ASA but or my 2620XM to monitor connections on a per-ip basis and prevent more than say 25 connections per minute per ip and block the offenders? I understand that I need to set something like a policy for this. Please help ,thanks.
0
Comment
Question by:eggster34
  • 3
  • 3
7 Comments
 
LVL 5

Expert Comment

by:MarkusKolbeck
ID: 17809969
what kind of mail server do you use? Maybe you can configure your policy there?

ATB
Markus
0
 

Author Comment

by:eggster34
ID: 17812903
it's merak server. I don't want the traffic to reach the server, though, I'd like to cut it on the perimeter without reaching the dmz.
0
 
LVL 32

Accepted Solution

by:
rsivanandan earned 500 total points
ID: 17813328
You can probably try the max connection limit with the tcp intercept for this server.

Check out this link;

http://www.ciscotaccc.com/kaidara-advisor/security/showcase?case=K18407732

In there, the '0' is what you want to modify.

Cheers,
Rajesh
0
PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

 

Author Comment

by:eggster34
ID: 17815532
What value do you think I should set this to?
If the attacker establishes 30 connections and the limit is 30 , can other clients reach the server at all?
0
 
LVL 32

Expert Comment

by:rsivanandan
ID: 17817168
This should be a trial and error eggster depends on your load on the server. Also 30 would be much lesser I believe.

Cheers,
Rajesh
0
 

Author Comment

by:eggster34
ID: 17830928
Any other way to do this? Can I get an IDS sensor for my ASA box that would do something like this?
0
 
LVL 32

Expert Comment

by:rsivanandan
ID: 17831800
hmm. Look for the SMTP signatures. I will check as well online (I don't have access to one though)

Cheers,
Rajesh
0

Featured Post

PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
windows 10 being blocked by AVG 3 63
Access shared drive during VPN session 9 108
iptables limit connection per ip correct way ? 2 140
Unblock a website in Cisco ASA 3 100
If you are like regular user of computer nowadays, a good bet that your home computer is on right now, all exposed to world of Internet to be exploited by somebody you do not know and you never will. Internet security issues has been getting worse d…
Do you have a windows based Checkpoint SmartCenter for centralized Checkpoint management?  Have you ever backed up the firewall policy residing on the SmartCenter?  If you have then you know the hassles of connecting to the server, doing an upgrade_…
This video shows how to use Hyena, from SystemTools Software, to bulk import 100 user accounts from an external text file. View in 1080p for best video quality.
Email security requires an ever evolving service that stays up to date with counter-evolving threats. The Email Laundry perform Research and Development to ensure their email security service evolves faster than cyber criminals. We apply our Threat…

770 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question