High named CPU every 10 minutes?

[blrmaani]

I see a peculiar behavior on my DNS server. The named CPU reaches 90%
+ every 10 minutes and my monitoring software keeps paging me.

I have a DNS host running FreeBSD 7.x, running BIND 9.4.x on a 2-CPU
machine with 4GB RAM. It is a recursive DNS server.

Any pointers on how to find out the reason for high CPU. I know that
this machine is not DDOSed

Thanks

Maani