Re: NAT external/Public IP

[Ansgar -59cobalt- Wiechers <bugtraq () planetcobalt net>]

On 2007-10-30 Security Incidents wrote:
> On 30 October 2007 07:04 PM Ansgar -59cobalt- Wiechers wrote:
> > On 2007-10-30 Grant Donald wrote:
> > > With PAT private IP addresses are hidden from the outside world.
> > > This basically makes the job of hacking into a system more
> > > difficult, because the original host's IP address and source port is
> > > unknown. 
> >
> > This is mere obscurity. It doesn't make a host any more or less
> > secure than it already is. Like I said before: either a host is
> > secure, then it doesn't matter if an attacker knows the address, or
> > it isn't secure, then you're "security" is based on the hope that an
> > attacker won't discover the host.
> >
> > > Depending on firewall capabilities (or lack of capabilities) ports
> > > may need to be opened inbound for certain applications to work
> > > (e.g.. ident & pptp). A horizontal scan of such a network could
> > > produce a wealth of knowledge, if that network does not support port
> > > address translation.
> >
> > Ummm... wot? Why would you want to allow any inbound connections into
> > your LAN? And how would an attacker be able to scan your network from
> > the outside? For some obscure reason you seem to assume that using
> > public IP addresses in your LAN means that the firewall at the
> > perimeter magically allows access from WAN to LAN. This assumption is
> > wrong.
>
> Why not Security by Design plus Security by Obscurity?

Because when you have security you don't need obscurity. It will only
add to the system's complexity, which in turn may even *reduce* security
(due to increased risk of misconfiguration and such).

> If the additional obscurity does not compromise the design, in any
> way, then we may in-fact end up with better security.

No, because it's not reliable, and it doesn't add to security in the
first place.

> Do you claim that you can make a host "secure"?

That depends on what you mean by "make a host secure". I do claim that
I'm able to identify security risks for a host, and define measures to
mitigate those risks in a reliable manner.

However, we're getting off the subject. I'm still waiting for someone to
explain how public addresses are any less secure than private addresses.
To repeat myself: using public addresses for hosts in your LAN does
*not* mean that those hosts automatically are publicly accessible.

Regards
Ansgar Wiechers
-- 
"All vulnerabilities deserve a public fear period prior to patches
becoming available."
--Jason Coombs on Bugtraq