ONI Section Two is a subdivision of the Office of Naval Intelligence.
During the Human-Covenant war, Section Two was responsible for releasing details of the SPARTAN-II program to the public to boost morale throughout the UNSC. Once information about the Spartans was released to the public, Section II had to maintain the Spartans' near-mythical. So they devised ONI Directive 930 to assist that. This directive made it so that no SPARTAN killed in action, would be listed as such. It was believed that news of Spartan deaths would cripple the UNSC's already-flagging morale.
Section Two is the propaganda branch of ONI. It handles communication between colonies to reduce the spread of rumors and information that would damage morale.