named: bad referral x from y?

[Mikko Kilpikoski]

Hi.

I'm getting a lot of following message in named log:
bad referral (x.x.x.x.in-addr.arpa !< *.x.x.in-addr.arpa) from [y.y.y.y].53

Where x is some host in a some network owned by X and y is my ISP's 
nameserver. I've gotten this message about two hosts from different 
networks. The networks in question are owned by same individual.

What does it mean? Should I be worried? Logcheck considers it a security 
violation. What can I do about it?

tia,
--
Mikko Kilpikoski