Make popa3d listen on specific interface

Lowell Gilbert freebsd-questions-local at
Sat Aug 16 08:53:06 PDT 2003

"Charles Howse" <chowse at> writes:

> Let me throw this in:
> This is a home network, behind a Cable Modem and 4-port Cable/DSL router
> w/ firewall.
> Port 110 is closed on the firewall.  Ports 80,20 and 21 are open on
> another machine in the DMZ.
> That said ( and I'm no expert ) wouldn't it be acceptable for *my*
> situation to bind to an address?
> That way, anyone wanting to crack into the pop server on this machine
> would have to get past the firewall, and then discover the address the
> pop server on this machine is listening on...? Nmap woud certainly do
> that, *if* they got in.
> I run a pop server on the Redhat machine next to the FreeBSD machine, no
> problems ever there.
> I could be way off on my logic, and my understanding of tcp/ip, so
> correct me if I'm wrong.

Not at all; you're dead on.  
The only thing I'm trying to warn you about is that binding to a
specific address is having a fairly small effect on your security in
this case.  For belt-and-suspenders protection, you'd be somewhat 
better off with a more sophisticated POP server which can bind to 
the inside interface directly instead of just the address.

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