Declassify Mission: Greatly reduced visibility
Kill the first set of enemies then head to the central room. You'll find a lot of ammo inside and three sentinel turrets. The declassify mission skull is also located outside of that room.
Like other survival missions, you have to dig in and place the sentinels in front of the stairs or doorways. The enemy composition will depend on your gameplay. Expect different types of locust reinforcements.
Getting this section's COG tag is a bit tricky. You have to wait for second wave to arrive since they'll be coming in from the door across the stairs where you found the last section's COG tag. You have to enter that door and you'll find the COG tag inside.
Later on, you'll have to fend off two Reavers. Just stay inside the room and take the riders out through the windows to avoid dying from the reavers' missiles.