A good way to reduce this is to turn off recursion for
people not on your network for your dns server. This is fairly easy
to do with bind8/bind9.
The attack isn't via recursive lookups (though recursion could help augment
the attack). The reflection is in terms of the DNS reply to the purported
requestor (really the victim). At lbl.gov, none of the requests result in
further lookups from our nameserver. But the victim still receives the reply
stream, which from a combined large number of name servers is very large.
See my draft paper
for a discussion of reflector attacks.