A "Big Game" was a colloquial expression, among Federation Starfleet line and flag officers -- and staff officers with need-to-know -- describing a "turf war" between two divisions of Starfleet, usually Starfleet Security and Starfleet Intelligence. These situations were unbeknownst to the general public and to most Starfleet personnel.
Despite the name, the potential cost of a "Big Game" could be in millions of lives. (Cloak and Dagger)
- identity checks every 50 metres in the ship's corridors
- access to high-level officers, such as the ship's commanding officer, were limited to those with an "alpha" clearance level
- all senior officers -- and all officers with access to sensitive areas such as the bridge, Main Engineering, sickbay, etc. -- were required to wear a security bracelet that recorded their whereabouts and even conversations. To remove the bracelet while the ship was under such a protocol would result in an officer's being charged with treason. At the least, said officer would undergo a hearing to determine whether their rationale for removing the bracelet with detrimental to Federation and Starfleet security.
- if the ship was berthed at a space station or dock, only the officers and crew aboard ship at the time the protocol was implemented had legal status to be on the ship until the protocol was lifted.