In the Computer Underground (CU), “ice” is a fictional form of anti-cracker countermeasure, often depicted as a wall of ice. The term first appeared in William Gibson’s book Neuromancer, in which he described various means of protecting systems from intrusion. In other words, IC was a software program on the Matrix to stop illegal access to company or government computer systems and valuable information stores. A number of intrusion countermeasure electronics types were available, including lethal Black IC—which could kill the intruder—and Probe IC, which hunted for system trespassers and then shot back.

Today, real world Intrusion Detection products, such as BlackICE, are modeled after the theoretical concepts. Nobody is killed and the shooting back—although technically illegal—targets the attacker’s computer system.

See Also: Matrix; Probe.