I had a situation a couple of days ago where a compromised machine in the DMZ 
portion of my network began sending an incredible number of queries to a couple 
of the primary internal DNS servers. The traffic was so intense that legitimate 
queries were unable to get through, or the customer timed out before the 
response came back. It took me a while to diagnose, because tailing the logs 
with querylog on was not possible. The data were coming too fast for my 
terminal to display them. Only after several Cntl-C commands was I able to 
escape from the tail, and a portion of the logs was displayed. Only queries 
from the compromised machine were visible. Nothing else got through during that 
time period. My customers and bosses are naturally furious.

So is it possible to limit the number of queries for one name from one client, 
or even better, limit the number in a certain time, or the number of queries 
"in a row" from one client. If not we are going to have to be creative with 
some iptables or firewall rules.

Thanks for any help you can lend.

Alan V. Shackelford                   Sr. Systems Software Engineer
The Johns Hopkins University and Johns Hopkins Medical Institutions
Baltimore, Maryland USA       410-735-4773        ashac...@jhmi.edu


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