KNOCKDNS

KNOCKDNS

A dynamic DNS service operated by tcp port knocking

Port knocking is a method of generating network authorisation for a source IP by making a sequence of TCP connections on particular port numbers to a host that is listening for them. Although usually used for opening firewalls and such, this alpha test implementation setting up dynamic DNS hostnames. The process for setting a dynamic hostname to a particular IP can be done as simply as a series of "telnet" connections to a sequence of port numbers, this can be easily scripted in pretty much any operating system. Linux even has a dedicated "knock" command to make it even easier.

For further technical information here are the Wikipedia entries on Port Knocking and Dynamic DNS.