Special Fleet Security

USR Special Fleet Security, better known as the Protectors, are a special forces branch of the Navy, who operate in concordance with crew of the ship and the embarked army personnel to provide protection in the event of ship-board raiding. They are also assigned to protect orbital and ground side facilities. Their role is two fold, in that they preform counter-boarding actions, fighting against enemy forces attempting to board their ships in close range, and counter terrorism, stopping terrorist attacks against the fleet. As such, they closely guard many facilities and ships with a vigilance not seen in many Sangheili. 
The Protectors are equipped with specialised Assault Harnesses, to give them enhanced endurance in close quarters fighting, where they most often expect to face the enemy. For armament, they often carry plasma rifles, repeaters, needlers, energy blades and energy knives, at ranges where these can be used to deadly effect. They often also carry Anti-Gravity packs into combat, to allow them to navigate outside the ship, and navigate damaged sections. They may also have some close dropship support and light vehicles, with heavy weapon support for groundside operations. 
Protectors are trained intensively in the disciplines of vigilance, stewardship, defence and observation, roles many young hot blooded Sangheili fail to grasp. However, they are deadly combatants, and often the sight of their purple armour is enough to turn back all but the most determined boarders, who know their steadfast defence is difficult to assail.