UNSC Military Security Code 447-R27
From Halopedia, the Halo wiki
United Nations Space Command Military Security Code 447-R27 is a UNSC protocol in effect in 2552. It forbids a consultant from accessing classified files in ONI's CASTLE Base on planet Reach. AIs guard the database against this. In event of an infraction, the offense is recorded and authorities are immediately notified. The AI then warns the infractee to stop, and is authorized to use whatever force necessary if the infractee will not comply, including killing[1].
