The contemporary term false flag describes covert operations that are designed to deceive in such a way that activities appear as though they are being carried out by individual entities, groups, or nations other than those who actually planned and executed them.
Lance deHaven-Smith states that “The term “false flag” originally referred to pirate ships that flew flags of the home countries of the ships they were approaching to attack and board. The pirates used the false flag as a disguise to prevent their victims from fleeing or preparing for battle. The term today extends beyond naval encounters to include countries that organize attacks on themselves and make the attacks appear to be by enemy nations or terrorists, thus giving the nation that was supposedly attacked a pretext for domestic repression and foreign military aggression.”
Operations carried out during peace-time by civilian organizations, as well as covert government agencies, can (by extension) also be called false flag operations if they seek to hide the real organization behind an operation.