Move your team into one of the chambers and start the mission by interacting with the node just inside the entrance. Once the mission is in progress a force field will activate preventing anyone from entering/leaving the chamber until the mission ends.
The force field in the center of the chamber will drop, and a named elite tactical ([x] of 12) will advance toward the node, while about half a dozen easy drones will also appear. Concentrate fire on the elite until its health is halfway down; it will retreat back to its original position leaving the players to mop up the drones. When the force field in the center of the chamber comes back up, you may be knocked back if you are too close.
On completion of the first phase, 4 heavy drones will be released from their force fields (one in each corner of the chamber) and advance down the ramps to the floor. Defeat them to continue to the next phase.
Once the heavies are out of the way, the elite tactical will advance again as it did in phase 1, this time supported by some plasma mortars. Stay mobile and concentrate fire on the elite, before deactivating the force fields protecting the three plasma mortars (in the middle of the raised platforms) so you can destroy them.
When the final phase is complete, the security codes will drop next to the start node. Pick them up to complete the mission.