In message <20090120233128.gi15...@isc.org>, "David W. Hankins" writes: > > --J+eNKFoVC4T1DV3f > Content-Type: text/plain; charset=us-ascii > Content-Disposition: inline > Content-Transfer-Encoding: quoted-printable > > On Tue, Jan 20, 2009 at 12:54:32PM -0800, Wil Schultz wrote: > > Anyone else noticing "." requests coming in to your DNS servers? > > > > http://isc.sans.org/diary.html?storyid=3D5713 > > I was surprised to see 'amplification' in the subject line here, since > on my nameservers my replies are of equal length to the queries. A > little bit of asking around, and I see that it is an amplification > attack, preying on old software. > > Let me sum up; > > If you're running 9.4 or later, you will reply to these packets with > 45 octet RCODE:Refused replies. 1:1. 9.4 has an "allow-query-cache" > directive that defaults to track allow-recursion, which you should > have set appropriately. > > If you're running 9.3 or earlier, you will reply to these queries > "out of cache" (the root hints), and those replies can be 300-500 > octets I think. 1:6-11. > > So in lieu of keeping a new up-to-date list of IP addresses to filter, > as it expands and shrinks, you can greatly reduce your own footprint > in these attacks with a quick upgrade. > > --=20 > David W. Hankins "If you don't do it right the first time, > Software Engineer you'll just have to do it again." > Internet Systems Consortium, Inc. -- Jack T. Hankins > > --J+eNKFoVC4T1DV3f > Content-Type: application/pgp-signature > Content-Disposition: inline > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v2.0.9 (GNU/Linux) > > iEYEARECAAYFAkl2XtAACgkQcXeLeWu2vmrR+wCePhZM2IrxV1mCKpnpsL6RDPIk > KnoAnRyVJpYrlan65MYJF7LRJc8nXJuj > =F1Dc > -----END PGP SIGNATURE----- > > --J+eNKFoVC4T1DV3f-- >
Or better yet trace the query traffic back to the offending source and implement BCP38 there. If the source won't implement BCP38 then de-peer them. It's time to take back the "commons". Mark -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: mark_andr...@isc.org
