[RndTbl] DNS Amplification DoS

[Paul Sierks]

Hey Everybody,

I recently saw iftop showing a couple "connections" of  ~200Kbps 
persistently on a box and because this wasn't the usual, I looked into 
it. Turns out it was caused by DNS lookups of type ANY ripe.net 
repeatedly. I can only assume this is an amplification attack. This box 
uses BIND 9.9.1-P3 is public facing and does recursive lookups (also 
authoritative). Now that that's out of the way, I'm looking/thinking of 
ways the prevent this obviously. This isn't causing a problem on a 100Mb 
link now but could get there quickly. As far as I know I don't have a 
lot of options, maybe iptables with some sort of limiting. ACLs would 
normally help, and would be perfect if I could get it to use a SQL 
database as the backend, and use that as a whitelist to at least 
mitigate the issue. If anyone has experience on the subject or an idea, 
it is much appreciated.

Regards,
Paul