In Sid Meier's Alpha Centauri (SMAC), the Hunter-Seeker Algorithm is a Secret Project. It may be built at a cost of 360 minerals, on discovery of Pre-Sentient Algorithms (D6). It negates ALL rival faction Probe Team operations against your faction's units and bases.

How useful is this? Probe operations are a significant part of the game; Probe immunity is a radical advantage. This is makes the Hunter-Seeker Algorithm one of those "must-build" Projects, as even your allies will occasionally send a Probe team your way to steal technology. The alternative is to station a defending Probe Team unit in every base. It also tempers the -2 Probe penalty incurred under the "Knowledge" model in the social engineering screen.

Secret Project animation narrative:
   "If I determine the enemy's disposition of forces while I have no perceptible form, I can concentrate my forces while the enemy is fragmented. The pinnacle of military deployment approaches the formless: if it is formless, then even the deepest spy cannot discern it nor the wise make plans against it."
   -- Sun Tzu,
   The Art of War, Datalinks