RE: IDS is dead, etc

["Bob Buel" <bob () buel org>]

Gentlemen:

Being a spectator to this discussion, I have to comment the obvious,
that in security, there can be no "perfectly implemented" anything. As
long as there is access to a system, there can be an attack. Your
firewall could be hacked. You can't say that there's not some
vulnerability that will be in tomorrow's news. You can't even say that
you won't have a hormonal inbalance on Monday morning, and alter that
"perfect implementation". How can you make your systems safe? Go to your
switch now and unplug all servers from their jacks. Are they safe now?
No, of course not, since they can still be accessed via console. Ok,
turn off the server, and put it in a vault behind a 7 foot concrete
bunker. Is it safe? Nope. Still can't say that. (Verisign unplugs their
root server, use a bunker, alarms, armed guards, and still won't ever
say it's safe!)
Sure, the odds are better, but whether or not your system will actually
be attacked is an equation byproduct of the attacker's motivation and
your safeguards. 
Now, if you will excuse the dialectical silliness of this rant, the
purpose of an NIDS is now clear--it is a reporting tool of what actually
did or try to happen on that network. 

Much as I appreciate the practicality of what you are saying, and agree
totally with it in an ideal sort of way, I can never say those thoughts
out loud where someone might hear it, because it is not a perfect world,
never will be, and I can't afford not to keep a watchful eye for
someone, sufficiently motivated, who will do the impossible!

Good day, gentlemen one and all,
and I have thoroughly enjoyed your discussion!

Bob


Subject: Re: IDS is dead, etc

2003-08-07T16:49:10 Barry Fitzgerald:
> Oh yes, and someone (perhaps tongue-in-cheek) mentioned that a
> properly configured firewall removes the need for an NIDS.

Perhaps you're referring to my comment:

        2003-08-06T14:57:53 Bennett Todd:
        > 2003-08-06T07:39:28 Paul Schmehl:
        > > Why would you want to know about Nimda attacks
        > > against your servers?
        >
        > (or more generally, attacks that won't succeed)
        >
        > Some people _don't_ care. They need to disable the
        > sigs they don't care about, or configure their IDS
        > to only match those sigs against servers for which
        > they're relevent.
        >
        > The limiting case of this argument says that given
        > a really perfectly implemented firewall, you don't
        > need an IDS at all. Some folks don't.

> I have to chime in and say that I couldn't possibly disagree more.

Understandable. I really shouldn't have included that remark; or
else I should have expanded on it. I didn't say "properly configured
firewall", I said "really perfectly implemented firewall", and I
meant something different by that, although I neglected to explain.

A perfectly implemented firewall allows no protocols through for
which there are vulnerable implementations inside. That means it's
impossible to implement a perfect firewall if you're going to allow
Windows users to have internet access. You can come moderately
close, with a hideous amount of work, but you'll still be very
exposed, and an IDS will be critical reinforcement of your flawed
security.

But given suitable systems configuration, it is possbile to have a
perfect firewall, and if you do then an IDS is just an educational
tool, and would probably be most useful in concert with a honeypot.

-Bennett


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