N.B.: The source code repository has been moved to GITHUB and will be removed from Google Code soonish

fpdns is a program that remotely determines DNS server versions. It does this by sending a series of borderline DNS queries which are compared against a table of responses and server versions.

False positives or incorrect versions may be reported when trying to identify a set of servers residing behind a load-balancing apparatus where the servers are of different implementations, when a specific implementation behaves like a forwarder, behind a firewall without statefull inspection or without Application Intelligence.