Black Ice
In the world of Netrunner, Black Ice refers to the most powerful and dangerous type of computer program that a corporation can use to protect its servers and data from unauthorized access by runners (hackers). Black Ice is designed to counter specific types of attacks and can inflict serious damage on runners who encounter it.
Each Black Ice program has a specific strength and a “subroutine,” which is a type of defensive action it can take when encountered by a runner. For example, some Black Ice subroutines might cause damage to the runner’s hardware or force the runner to discard cards from their hand.