North American Network Operators Group

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

Re: To CAIS Engineers - WAKE UP AND TAKE CARE OF YOUR CUSTOMERS

  • From: Pyda Srisuresh
  • Date: Tue May 15 12:08:12 2001

--- [email protected] wrote:
> On Mon, 14 May 2001 23:18:09 PDT, Adam McKenna <[email protected]>  said:
> > It does hurt.  It causes non-obvious problems.  Forcing hostnames and PTR's
> > to match (commonly referred to as PARANOID checking) does not provide extra
> > security, it just prevents people with badly configured DNS from accessing
> > your servers.
> 
> I once did a similar check in a Sendmail configuration, and found it to be
> incredibly useful in reducing the spam load without significantly impacting
> actual traffic.
> 
> There's a second-order effect here - the sort of clueless ISP that is unable
> to get a PTR entry correct is *ALSO* the sort of clueless ISP that is very
> likely unable to detect/eliminate hacker/spammer/etc nests in their address
> space.
> 
> You of course need to be sure that your *own* DNS is rock-solid and up to
> date (although our departmental network liaisons that maintain their zones
> have learned that Things Will Not Work if they don't do it right ;).  You
> also need to apply the usual skepticism for results - there *could* be a
> temporary outage, for instance.
> 

Forcing hostnames and PTR's to match will also prevent people from NAT
land accessing your servers. There are hardly any NAT implementations
that do dynamic DNS updates. 

> It's *NOT* a security measure to deploy by itself.  It's however useful as
> Yet Another Part of a Complete and Balanced Security Breakfast... ;)
> 

Only if you consider keeping up-to-date PTR records and dynamic DNS updates
a security measure.

> -- 
> 				Valdis Kletnieks
> 				Operating Systems Analyst
> 				Virginia Tech
> 
> 

cheers,
suresh

__________________________________________________
Do You Yahoo!?
Yahoo! Auctions - buy the things you want at great prices
http://auctions.yahoo.com/