From Halopedia, the Halo wiki
Office of Naval Intelligence
Field Officer 345-261b was an Office of Naval Intelligence operative stationed at the UNSC headquarters on the planet Reach. As per the WINTER CONTINGENCY Declaration Supplemental Orders, the individual was required to redact all XNAV and ASTRONAV data on the planet after the declaration of WINTER CONTINGENCY.
The officer's real name, rank, and gender are unknown.