The Imperial Secret Service. It had been long-standing policy of the Roman legions and armies of occupation to utilize informers and spies, but never in an organized fashion, even in the city of Rome, with its whispers and endless conspiracies. Titus used the special messengers and assassins of the Praetorian Guard to carry out executions and liquidations (the Speculatores ); however, they belonged to the Guard and were limited in scope and power.

By the 2nd century A.D. the need for an empire-wide inteligence service was clear. But even an emperor could not easily create a new bureau with the express purpose of spying on the citizens of Rome's far-flung domains. A suitable compromise was found by Hadrian. He envisioned a large-scale operation and turned to the frumentarii. The frumentarius was the collector of corn in a province, a position that brought the official into contact with enough locals and natives to acquire considerable intelligence about any given territory. Hadrian put them to use as his spies, and thus had a ready-made service and a large body to act as a courier system. The story was told that the frumentarii read a letter addressed to a man in goverenment in the provinces who, according to his wife's correspondence, loved only baths and pleasures. When the official requested a furlough, Hadrian was able to tell him not to be so fond of leisure.

The frumentarii quickly earned the hatred of society. In the 3rd century, association with the heads of the service could produce severe repercussions. In 217, Macrinus appointed Marcus Oclatinus Adventus, the former heads of the frumentarii and the prefect of the Praetorian Guard to the Senate. With one decision, Macrinus alienated most of the Roman establishment and made his own political destruction inevitable-- so much were the frumentarii resented. Diocletian terminated the frumentarii because of their abuses and loathsome reputation. The emperor's decision netted him great popularity, but a short time later the equally sinister and far better organized agentes in rebus made an appearance.