dopp at acm.cs.umn.edu wrote:
> 
> I'd guess someone is tryng to exploit you.  I'd say let it through and,
> on your firewall, route it to a blackhole.
> 
> Gabe
> 
> On Wed, Nov 22, 2000 at 08:19:35AM -0600, Clay Fandre wrote:
> > I'm getting tons of denies on my firewall/Masq box on my DSL line which
> > is using IPChains to filter out almost everything. I want to make it
> > stop because it's filling up my logs. (No, I don't want to turn of
> > logging) I'm assuming it's doing a DNS query since it's coming from port
> > 53, but don't really know why. My firewall box is a DNS server, but only
> > for my internal non-routable network. Anyone have any ideas?
> >

Actually if I would have paid closer attention to the logs I would have
notices that my system was denying return request packets from a request
my machine was sending out. (Doing a tcpdump confirmed this thought.) I
checked my ipchains rules and DID have a hole opened up for DNS
responses, so why was it being denied? Then I looked at the error
message, which contains the IPChain rule #.
Nov 22 09:38:10 maddog.matrix.comp kernel: Packet log: input DENY eth1
PROTO=17 217.24.32.10:53 64.6.191.90:1030 L=182 S=0x00 I=29240 F=0x0000
T=47 (#32)

And then I found it. Rule #32:
DENY       all  ----l-  217.0.0.0/8          anywhere              n/a

This used to be a IANA reserved address range, which is why I deny it. 
But after checking out the IANA site, I found out that it was changed in
June 2000.

http://www.isi.edu/in-notes/iana/assignments/ipv4-address-space

If anyone else has this rule in your firewall config you might want to
remove it.