DNS SURVEYS

An ongoing survey that searches for open DNS resolvers.

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.

• October 2010
• October 2009
• October 2008
• October 2007
• August 2006
• June 2005

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 and TTL values
• Have mismatched serial numbers
• Utilize IPv6
• Utilize DNSSEC
• Publish SPF records or have DKIM configured
• Support 0x20

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.

A survey that searched for DNS cache poisoners.