Re: Ok; let's have the "Does DNAT contribute to Security" argument one more time...

[Cameron Byrne <cb.list6 () gmail com>]

On Nov 14, 2011 9:22 PM, <Valdis.Kletnieks () vt edu> wrote:
> On Mon, 14 Nov 2011 19:06:13 EST, William Herrin said:
>
> > Using two firewalls in serial from two different vendors doubles the
> > complexity. Yet it almost always improves security: fat fingers on one
> > firewall rarely repeat the same way on the second and a rogue packet
> > must pass both.

Complexity equals downtime. I know at least one definition of security
includes availability .

> Fat fingers are actually not the biggest issue - a far bigger problem are
brain
> failures.  If you thought opening port 197 was a good idea, you will have
done
> it on both firewalls.  And it doesn't even help to run automated config
> checkers - because you'll have marked port 197 as "good" in there as
well. ;)
> And it doesn't even help with fat-finger issues anyhow, because you
*know* that
> if your firewall admin is any good, they'll just write a script that
loads both
> firewalls from a master config file - and then proceed to fat-finger said
> config file.

And, stateful firewalls are a very common dos vector.  Attacking firewall
sessions per second capacity and blowing up a session table can bring a
service down real quick. Furthermore, firewalls are frequently installed at
a choke point ... Which makes them a topological single point of
failure.... So, they are deployed in pairs .... And therefore have a nice
cascading failure behavior when hit with a dos.

Cb