False Flag is a concept that goes back centuries. It was considered to be a legitimate ploy by the Greeks and Romans, where a military force would pretend to be friendly to get close to an enemy before dropping the pretense and raising its banners to reveal its own affiliation just before launching an attack. In the sea battles of the eighteenth century among Spain, France and Britain hoisting an enemy flag instead of one's own to confuse the opponent was considered to be a legitimate ruse de guerre, but it was only "honorable" if one reverted to one's own flag before engaging in combat.
Today's false flag operations are generally carried out by intelligence agencies and non-government actors including terrorist groups, but they are only considered successful if the true attribution of an action remains secret. There is nothing honorable about them as their intention is to blame an innocent party for something that it did not do. There has been a lot of such activity lately and it was interesting to learn by way of a leak that the Central Intelligence Agency (CIA) has developed a capability to mimic the internet fingerprints of other foreign intelligence services. That means that when the media is trumpeting news reports that the Russians or Chinese hacked into U.S. government websites or the sites of major corporations, it could actually have been the CIA carrying out the intrusion and making it look like it originated in Moscow or Beijing.