The Art of Unspoofing – Describes several methods to track down denial of service attacks and includes a patch for Bind v8.3.3 and 4.9.9 which adds logging of external queries regarding domains the nameserver is authoritative for.
You can download it from the following link: https://packetstormsecurity.com/files/download/29643/unspoofing.txt
Source: https://packetstormsecurity.com/files/29643/unspoofing.txt.html