Firewall Wizards mailing list archives
Re: Corporate H/N IPS
From: Crispin Cowan <crispin () wirex com>
Date: Sat, 14 Dec 2002 14:16:25 -0800
Talisker wrote:
Crispin I'm not exactly in agreement with many of your points
No worries; that's what forums like this are for :)
Neither would I. I'm not saying that products marketed as NIPS make *good* firewalls. In particular, they are incomplete firewalls, because they don't have the classical capability to block on IPs, ports, & such. Conversely, one could also say that classical packet filters are also incomplete, because they don't look at high level application traffic. The composition of the two adds value to make a more complete firewall system.EXACTLY like a firewall, only they look at higher level aplication protocols than classic packet filtering firewalls.I for one would not entrust my perimeter defense to a NIPS, however I may consider using a NIPS to look for intrusion signatures on those packets that have been passed by the firewall. I feel they complement each other very well.
None of which is new: ancient firewall design calls for an outer firewall defend your DMZ, and an inner firewall to defend your LAN. These firewalls would often be of different design, e.g. a packet filter on the outside and a proxy firewall on the inside.
To be clear, my claim is not that NIPS suck. My complaint is that the claim that NIPS is a bold new concept is crap, and that NIPS should properly be understood as an incremental improvement in firewall technology.
Again, this is an incremental improvement on an old concept. A retro-fit security enhancement package fitted onto an existing OS to make it a secure OS. Olde schoole secure OS people will rant about how much less cost-effective it is to retro-fit security, and they may be right, but that's what it is. We built one (Immunix) because I thought it was interesting, and because the economics of the cost of wholesale replacement of operating systems dwarf the cost benefits of designing in security vs. retrofitting it.I do see HIPS as different from Secure OS's they are more widely available to all, deployable with minimal impact on an existing network and enterprise aware out of the box.
Again, I'm not saying that IDS has no value, just that its value needs to be understood. Both Intrusion Preventers and Intrusion Detectors are looking at traffic/operations, and trying to distinguish good from bad. If the distinction can be done precisely (nearly zero false positives) and in real time (before the traffic/operation completes) then it can be used for access control. If the distinction is heuristic (has a real false positive rate) or is slow (makes the distinction long after the traffic/operation completes) then you use it for detection instead of prevention.True: "intrusion detection" is what you call it when your detector is so slow or imprecise that it cannot be used for prevention.IDS can be a little hit and miss, I've had to switch some off because they were so inadequate. However, I have also used others to good effect they have saved my network on many occasions.
The trade off for detection is that detectors can detect much more subtle intrusions. They can infer attacks comprised of legitimate operations that would have passed access control. They can spend more time on analysis. This is why you have detection in addition to your access controls/prevention stuff.
Crispin -- Crispin Cowan, Ph.D. Chief Scientist, WireX http://wirex.com/~crispin/ Security Hardened Linux Distribution: http://immunix.org Available for purchase: http://wirex.com/Products/Immunix/purchase.html Just say ".Nyet"
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Current thread:
- Corporate H/N IPS Talisker (Dec 13)
- Re: Corporate H/N IPS Crispin Cowan (Dec 13)
- Re: Corporate H/N IPS Carson Gaspar (Dec 14)
- Re: Corporate H/N IPS Talisker (Dec 14)
- Re: Corporate H/N IPS Crispin Cowan (Dec 14)
- Re: Corporate H/N IPS Fritz Ames (Dec 15)
- RE: Corporate H/N IPS Bill Royds (Dec 15)
- RE: Corporate H/N IPS David Lang (Dec 16)
- Message not available
- RE: Corporate H/N IPS Marcus J. Ranum (Dec 17)
- Re: Corporate H/N IPS Crispin Cowan (Dec 13)
- <Possible follow-ups>
- Re: Corporate H/N IPS Chris Boscolo (Dec 16)
- Re: Corporate H/N IPS Marcus J. Ranum (Dec 17)