Antibody

Antibodies formed part of the immune system of a lifeform, fighting off foreign bodies and preventing disease. Several species applied this concept to machines.

The Great City of the Exxilons created antibodies to defend itself. (TV: Death to the Daleks)

The human-crewed robotic ship, Teselecta, which fittingly appeared as a humanoid, was guarded by an internal system of antibodies which eliminated unauthorised personnel. (TV: Let's Kill Hitler)

The Dalekanium casings which housed the Daleks were similarily protected by a system of antibodies which, as described the Twelfth Doctor, "hoovered" miniaturised intruders into liquid protein which was transferred into the Dalek's feeding tubes. (TV: Into the Dalek)