We hit half-million: The Cidr Report

Robert Drake rdrake at direcpath.com
Thu May 1 22:00:45 UTC 2014


On 4/29/2014 10:54 PM, Jeff Kell wrote:
> Yeah, just when we thought Slammer / Blaster / Nachi / Welchia / etc /
> etc  had been eliminated by process of "can't get there from here"... we
> expose millions more endpoints...
>
> /me ducks too (but you know *I* had to say it)
>
Slammer actually caused many firewalls to fall over due to high pps and 
having to track state.  I thought about posting in the super-large 
anti-NAT/statefull firewall thread a few weeks ago but decided it wasn't 
worth it to stir up trouble.

Here is some trivia though:

Back when Slammer hit I was working for a major NSP.  I had gotten late 
dinner with a friend and was at his work chatting with him since he 
worked the night shift by himself.  It became apparent that something 
bad was wrong with the Internet.  I decided to drive to my office and 
attempt to do what I could to fix the issues.

This was a mistake.  Because of corporate reasons, my office was in a 
different city from the POP I connected to.  I was 3 hops away from our 
corporate firewall, one of which was a T1.

We had access lists on all the routers preventing people from getting to 
them from the Internet, so I thought my office was the only place I 
could fix the issue.  Well, someone had put a SQL server in front of or 
behind the firewall, somewhere where it would cause fun.  That DOS'd the 
firewall.  It took 3-4 hours of hacking things to get to the inside and 
outside routers and put an access-list blocking SQL.  Once that was done 
the firewall instantly got better and I was able to push changes to 
every 7500 in the network blocking SQL on the uplink ports.

This didn't stop it everywhere because we had 12000's in the core and 
they didn't support ACLs on most of the interfaces we had.  The access 
lists had to stick around for at least 6 months while the Internet 
patched and cleaned things up.

Fun fact:  the office network I was using pre-dated RFC1918 so we were 
using public IPs.  The software firewall that fell over either did so 
because statefull rules were included for SQL even when they weren't 
needed, or it died due to pure packets/sec.  Regardless, all of the 
switching and routing hardware around it were fine.

This isn't an argument against firewalls, I'm just saying that people 
tend to put stock in them even when they're just adding complexity.  If 
you have access lists blocking everything the firewall would block then 
you might think having both gives you defense in depth, but what it also 
does is gives a second place where typos or human error might cause 
problems.  It also gives a second point of failure and (if state 
synchronization and load-balance/failover are added) compounded 
complexity.  It depends on the goals you're trying to achieve.  
Sometimes redundant duties performed by two different groups gives you 
piece of mind, sometimes it's just added frustration.



More information about the NANOG mailing list