From Halopedia, the Halo wiki
The Overwatch network, also referred to as the "core authority"[Note 1] is a general term used to regard the collective core security and transit authorities of the Forerunner Ecumene. The overwatch network monitored, rationed and forbade travel to limit the buildup of reconciliation debt in the galaxy. Guardian Custodes were able to connect to the overwatch network, using it to reflexively counter many potential threats to the Ecumene long before they came to the attention of Warrior-Servant commanders. The Didact noted that they could track slipspace journeys if they were rational, while irrational series of jumps were harder to track. He used this to an advantage while on the run from the Forerunner authorities shortly after he was revived from his exile in a Cryptum.
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