port knocking(p��rt nok´ing) (n.) A method of establishing a connection to a secured network or computer within a network that does not have an open port. A remote device sends a series of series of connection attempts, in the form of packets, to the computer��s closed ports, and the attempts are silently ignored but logged by the firewall. When the remote device has established the predetermined sequence of port connection attempts, a daemon triggers a port to open, and the network connection is established. This security method is analogous to knowing a "secret knock," and only people who know the proper knock sequence will be allowed access. An advantage of using a port knocking technique is that a malicious hacker cannot detect if a device is listening for port knocks.
Other forms: port knock (n.), (v.)