DNS SURVEYS

Open Resolvers

An ongoing survey that searches for open DNS resolvers.

Cache Poisoners

An ongoing survey that searches for DNS cache poisoners.

April 2005: Number of Nameservers

We probed 5% of routed IPv4 space, or 70 million addresses, looking for nameservers. For those that replied, we also tried to determine their software and version.

Zone and Nameserver Statistics

With these surveys we send queries to 1,000,000+ zones and their authoritative nameservers looking for zones and nameservers that:

Advertise their software version
Allow recursion
Allow zone transfers
Exist on the same subnet
Have delegations which differ from authoritative NS records
Have lame delegations
Have questionable SOA values
Have mismatched serial numbers
Utilize IPv6
Utilize DNSSEC
Publish SPF records

We also query a random 5% sample of routed IP addresses to look recursive resolvers and determine whether or not they openly provide service to anyone, and what software they are running.