[CLUE-Tech] How good is NAT security?

[David Anselmi]

When I got DSL, I was worried that having my computer on line whenever
it was on made me extra vulnerable to Internet attacks.

It seems though, that since my DSL modem is doing NAT, and I'm not
forwarding any ports from outside to inside, that I should be pretty
secure - even without a firewall.

The only thing visible from the outside, seems to me, should be the
modem itself (which I've set up a filter to block traffic from the wan0
interface), and maybe some ports that I've gone out on and are in the
NAT table.

So I feel pretty good about not running a firewall (at least until I
want to open up port forwarding to allow access to a server).

Am I really naive, or is this pretty close?  I don't dispute that an
extra layer would be nice (especially since I'd like more visibility
into what's coming and going).

I also don't dispute that the modem could be hacked to open everything
up.  Has anyone heard of such an exploit?

Dave