OBS – Croatia's intelligence agency, the Obavestajna Bezbednostna Sluzba.

OP – observation post.

OFFENSIVE PENETRATION OPERATION – infiltration of an agent into a target group or organization.

OFFSITE – a covert FBI site or facility situated away from a field office.

OG – an acronym for original gangmembers, now in their thirties and forties, who supply cocaine and heroin to street gangs.

ONE-TIME PAD – an unbreakable code system that works by adding the numeric value of the plaintext with a randomly-generated code string (the one-time pad). Also see FIBONACCI SYSTEM.

OPEN-SOURCE - intelligence gained from public materials.

OSA – official secrets act, usually a law to enable governments to conceal their mistakes from their own population.

OSINT -: open source intelligence; an all-source process which includes HUMINT, IMINT, SIGINT, and MASINT which analysts must understand and integrate to produce the best possible intelligence.

OSS - Office of Strategic Services; U.S.'s WWII intelligence, sabotage, and subversion organization

OUTRIDER – a wheel artist responsible for ensuring that the target does not get outside the floating box of surveillance vehicles. See also FLOATING BOX.

OVERT TARGET – deliberately attempts to draw attention and drain the resources of an intelligence agency or security service. Occasionally a decoy.