repeated req: nlookup(aol.com) type=15 class=1

[Mark Kent]

Hello,

I have observed repeated queries to our listed(*) nameservers
of this type:

 datagram from [129.180.11.17].13386, fd 24, len 25; now Wed Jul 28 10:50:46 1999
 req: nlookup(aol.com) id 43341 type=15 class=1
 req: found 'aol.com' as 'aol.com' (cname=0)
 ns_req: answer -> [129.180.11.17].13386 fd=24 id=43341 size=500 Remote

These are coming in at about 1 or 2 a second from a dozen hosts
spread out around the net.  None of these hosts should be pointing
at our nameservers for routine name lookups, and of course we are
not authoritative for aol.com.

All are type=15 (MX record).

The requests are coming from:

Name:    janker.wankermobile.org
Address:  216.41.23.68

Name:    Lets.lepak.net
Address:  216.15.178.201

Name:    crow.prod.itd.earthlink.net
Address:  209.178.63.7

Name:    cardassian.keysdigital.com
Address:  208.235.124.20

Name:    mcls.rochester.lib.ny.us
Address:  204.97.3.3

Name:    wks01.spo.embratel.net.br
Address:  200.245.255.33

Name:    inspire3d.com
Address:  199.108.32.203

Name:    sss00204.schwab.com
Address:  162.93.15.131

Name:    turing.une.edu.au
Address:  129.180.11.17

and 203.251.77.1 (somewhere in Korea).

I am going to block these out, but I was wondering what would case
such behavior?  They are all asking the same question, of the wrong
servers, and repeating it over and over and over...

Thanks,
-mark

(*) By "listed" I mean servers that at least one NIC lists as
    authoritative for some zones.