Distinct from assassination, which may or may not be performed by an intelligence agency, counterassassination is nearly always a black op. The general course of a counterassassination goes something like this:

• Someone important to Nation X is marked for death by Nation Y.
• Nation X finds out, through espionage such as a double agent, or a wiretap.
• Nation X then hunts the hunter, and assassinates the assassin before the killing can take place.