These are the ranks of the Overwatch Transhuman Arm. This will help you understand the whitelist better.
Overwatch Soldier (OWS) Edit
The bulk of the OTA. They are tasked with everything from prison guarding to handling crises situations. Most of the time, these units are in the stasis until required. Can usually be seen using your basic MP7 or AR2.
Overwatch Soldier Captain (OWC) Edit
This one really isn't needed, but they are basically the shotgun soldiers (Or ShotGunners) from Half Life 2. There should be at least 1 of these units in a standard raid. They can also command OWS. They may also use the OSIPR (AR2, Irifle), but they cannot use the dark energy ball. If not raiding, these units lead OWS into battle.
Elite Overwatch Soldier (EOW, EOS) Edit
So you wanna know about the big boys now? Well, these units are specially authorized to use the OSIPRs(Overwatch Standard Issue Pulse Rifle) secondary fire, the dark energy ball, which they fire with deadly acuracy. They inflict more overall damage then regular soldiers do, and take around 2 or 3 more hits then regular soldiers aswell. These units are tasked with leading strike teams (1 EOW, 1 OWC, 2 OWS) into battle or raids. Generally not called out unless they are really needed, most of the time the leadership is played by the Captains.