limiting number of recursion/queries per IP address

[Kebba Foon]

Dear List,

Is is possible to limit the number of recursion/queries per IP address.
there is some kind of virus thats bombarding my dns servers with a lot
of queries, i realize that when ever the total number of recursion
clients reach 1000 dns resolution stop working. i have increase the
recursive-clients to 10000 but still these those not help. and also i
have increase the number of max open files on my OS which at one point
was complaining about too many open files. can someone please direct me
to how best to solve this problem its some kind of DDOS.

Thanks
Kebba