And what about blocking fragmented packets entirely. I would argue
that this would be an acceptable config on many networks.
Jack
On Thu, 16 Sep 2004 23:30:30 -0400, Tony Carter <tcarter@entrusion.com> wrote:
David,
Can you back your claim that IPS can easily be evaded by fragging
packets? Have you actually tested this or is it your guess?
-Tony
On Sep 12, 2004, at 12:29 AM, David Maynor wrote:
Yeah....I am gonna go ahead and disagree with you on some of these.
I have seen a lot of discussion about the differences between IDS,
IPS, and firewalls and the potential for convergence, but I do not
recall a discussion on the primary features that an IPS should have
out of the box.
I am thinking of:
- Flow Control - limitations on flooding, unused connections, etc...
Most of this should be handled by the signature base.
- Robust, ACURATE signature base
Only way to do this and not create tons of false postives is true
protocol parsing. This knocks out most IPS vendors like Tipping Point.
- Packet capture - no debate on how much before, as that has been
covered
- Pre-deployment network analysis tools to accelerate deployment
- Anomaly detection
Why? I have yet to see a system that is more than a parlor trick.
Anomaly based system are even easier to evade than sig based systems
that don't do protocol parsing.
What I would add is better tools for testing. Almost nobody grabs a
copy of Canvas from Immunity or Impact from Core and actually checks
what attacks are caught. Further more an even fewer number use modded
copies of public exploits to see if the claims made by vendors are
actually true. How many vendor's IPS implementation would actual catch
a MS03-026 exploit if you frag at the RPC layer at a size like 8
bytes?
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