New type of DDoS? Anyone saw it?

[Marek Królikowski]

Hello,
I was thinking to block only client who do attacks something like this:
/sbin/iptables --insert INPUT -s IP-ADDRESS-CLIENT-WHO-ATTACK -p udp --dport 
53 -m string --from 40 --to 80 --algo bm --hex-string '|somethinghere|' -j 
DROP -m comment --comment "DROP DNS AAAA DDoS"

Anyone know how must look proper iptables --hex-string to block all AAAA 
with IP address: AAA.BBB.CCC.DDD

Best Regards
Marek



In message <e7f58592-1570-494f-a530-97e54b8c04cf at rrcic.com>, "John W. 
Blue" writes:
>
> Hello Marek,
>
> Do you have an IPv6 assignment?  If not, there is really no need to even
> be resolving AAAA records.  An overly simplistic description of a
> potential solution could be to just drop the incoming AAAA request via
> its hex value in much the same way rate limiting is done for the "any"
> query:
>
> -hex-string '|0000FF0001|'
>
> I don't know off hand what the hex value for AAAA is but it should not be
> too hard to find.
>
> John

Just dropping AAAA queries is a bad idea as most machines actually
have a AAAA addresses (loopback and linklocal) so just about every
application makes AAAA queries.  If you drop AAAA queries you slow
up every address lookup in your network.

Mark
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org