Snort mailing list archives
RE: IDS Placement ideas for inside and outside a firewall.
From: "Brian Laing" <Brian.Laing () Blade-Software com>
Date: Fri, 4 Apr 2003 07:42:49 -0800
Having this sort of implementation can do a couple of things. First off it can greatly reduce the amount that one sensor is looking at, since it only has to keep up with what's going into and out of the firewall. The bits that you are missing is internal machines attacking internal machines, internal machines running unwanted services, unknown access points into the network, etc. I have seen some customers who don't care about that, while most do. The difficulty is even if you want to look for all that stuff it can be difficult to impossible to place a single or small number of sensors in an efficient manner to catch all this traffic. If you like you can drop me a line and we can chat off line I would be happy to look at a network diagram and make some recommendations. Cheers, Brian ------------------------------------------------------------------- Brian Laing CTO Blade Software Cellphone: +1 650.280.2389 Telephone: +1 650 367.9376 eFax: +1 208.575.1374 Blade Software - Because Real Attacks Hurt http://www.Blade-Software.com ------------------------------------------------------------------- -----Original Message----- From: snort-users-admin () lists sourceforge net [mailto:snort-users-admin () lists sourceforge net] On Behalf Of Ponte, Paul F Sent: Thursday, April 03, 2003 7:04 PM To: 'snort-users () lists sourceforge net' Subject: RE: [Snort-users] IDS Placement ideas for inside and outside a firewall. Hi all - I'd like to ask your opinions on one part of this question. When we talk about a sensor on the inside of the firewall, I assume that means it can see all traffic on the internal subnet. But what do you give up if you monitor just traffic passing on a VLAN between the firewall and the router sitting between it and the rest of the network? Is this a valid installation? What's the danger in not monitoring all of the normal host to host traffic on your network which doesn't need to cross the firewall? I'm considering this kind of deployment, so thanks for your opinions on this. Paul -----Original Message----- From: Brian Laing [mailto:Brian.Laing () Blade-Software com] Sent: Thursday, April 03, 2003 5:58 PM To: 'Brei, Matt'; 'David Glosser'; 'FWAdmin'; snort-users () lists sourceforge net Subject: RE: [Snort-users] IDS Placement ideas for inside and outside a firewall. It can help, but I would not rely on it for prosecution the fact is the data is too easy to spoof and is not collected in a forensically sound manager either at the sensor or the management console. By forensically sound I mean certified to be free from tampering. Not that this data wont help your case, but its better to rely on it to see where and into what else the attacker may have gotten into. ------------------------------------------------------------------- Brian Laing CTO Blade Software Cellphone: +1 650.280.2389 Telephone: +1 650 367.9376 eFax: +1 208.575.1374 Blade Software - Because Real Attacks Hurt http://www.Blade-Software.com ------------------------------------------------------------------- -----Original Message----- From: Brei, Matt [mailto:mbrei () medclaiminc com] Sent: Thursday, April 03, 2003 2:18 PM To: brian.laing () blade-software com; David Glosser; FWAdmin; snort-users () lists sourceforge net Subject: RE: [Snort-users] IDS Placement ideas for inside and outside a firewall. That's exactly why I would want one outside of the firewall. If I were to find a successful break in, I could then review logs from the external IDS and find that the same IP had done several scans or whatever that were eventually blocked by the firewall and not picked up by the internal IDS. I would think that this would help build a better case if any type of legal action were to be taken. Matt -----Original Message----- From: Brian Laing [mailto:Brian.Laing () Blade-Software com] Sent: Thursday, April 03, 2003 11:28 AM To: 'David Glosser'; Brei, Matt; 'FWAdmin'; snort-users () lists sourceforge net Subject: RE: [Snort-users] IDS Placement ideas for inside and outside a firewall. I would agree with this sort of implementation, in many of the installs I have done I will setup the external sensors to do nothing but logging and ignore the data till I see something worth looking at on one of the internal servers. I use this data to see what else that IP has been doing or what other things have been attempted against a specific host ------------------------------------------------------------------- Brian Laing CTO Blade Software Cellphone: +1 650.280.2389 Telephone: +1 650 367.9376 eFax: +1 208.575.1374 Blade Software - Because Real Attacks Hurt http://www.Blade-Software.com ------------------------------------------------------------------- -----Original Message----- From: snort-users-admin () lists sourceforge net [mailto:snort-users-admin () lists sourceforge net] On Behalf Of David Glosser Sent: Wednesday, April 02, 2003 11:10 PM To: Brei, Matt; FWAdmin; snort-users () lists sourceforge net Subject: Re: [Snort-users] IDS Placement ideas for inside and outside a firewall. If you've never set up any IDS before, I'm not sure you would want to place it outside your firewall immediately You'lll get overwhelmed with probes,scans, script kiddies etc. First place the box (with the "snorting" NIC unnumbered). On the port monitoring the *internal* interface of your firewall. Let it work on all of the stuff your firewall lets through. Once you have that under control, then place another box (or another NIC on the same box) to monitor your internal servers (since breakins can come from internal users). Once you have these two under control, then you can worry monitoring stuff outside the firewall, which I believe is called *attack detection*. But do you care that much about the stuff your firewall is successfully blocking? --snip- I am trying to convince my company to implement IDS on our network but I have a few questions. I know I would want one on both sides of the firewall, The International Fund for Animal Welfare (IFAW -- www.ifaw.org) works to improve the welfare of wild and domestic animals throughout the world by reducing commercial exploitation of animals, protecting wildlife habitats, and assisting animals in distress. IFAW seeks to motivate the public to prevent cruelty to animals and to promote animal welfare and conservation policies that advance the well-being of both animals and people. This transmission is intended only for use by the addressee(s) named herein and may contain information that is proprietary, confidential and/or legally privileged. If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution, or use of the information contained herein (including any reliance thereon) is STRICTLY PROHIBITED. 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Current thread:
- RE: IDS Placement ideas for inside and outside a fi rewall. FWAdmin (Apr 02)
- <Possible follow-ups>
- RE: IDS Placement ideas for inside and outside a fi rewall. FWAdmin (Apr 02)
- RE: IDS Placement ideas for inside and outside a fi rewall. Philip Davidson (Apr 02)
- RE: IDS Placement ideas for inside and outside a fi rewall. FWAdmin (Apr 03)
- RE: IDS Placement ideas for inside and outside a fi rewall. Ponte, Paul F (Apr 03)
- Re: IDS Placement ideas for inside and outside a firewall. David Glosser (Apr 03)
- RE: IDS Placement ideas for inside and outside a firewall. Brian Laing (Apr 04)