North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: Telco's write best practices for packet switching networks

  • From: Steven M. Bellovin
  • Date: Thu Mar 07 16:54:38 2002

In message <[email protected]>, Sean
 Donelan writes:
>My comment was originally prompted by the meeting minutes which
>reported on the survey data showing that 100% of carriers are implementing
>firewalls in their gateways.  The 100% is what caught my eye.  As the
>topic comes up in various places, large ISPs repeatedly say they are
>unable to implement filters or packet screening on their high-speed
>links such as at peering points.  So the self-reported 100% implementation
>of screening and filtering firewalls at gateways didn't seem to jive
>with my understanding of the limitations faced by large ISPs.

>Firewalls can be a useful tool in the security engineer's toolbox.  But
>they get misused a lot.  I don't believe security engineers are better
>programmers.  If there was a class of programmers in the world that didn't
>make mistakes, I would hire them to write the applications. When the
>firewall is more complex than the application server it is "protecting"
>which is likely to have more mistakes?
Yes and no.  I don't think that security programmers are any better 
than application programmers.  But they might be trained differently.  
For example, I suspect that most application programmers have never 
heard of format string vulnerabilities.  I would hope that most 
security professionals have.

But you're absolutely right about the complexity of many of today's 
firewalls -- I've been complaining about that for years.

		--Steve Bellovin,
		Full text of "Firewalls" book now at