Security drones (a.k.a. Junk bots, since they drop scrap which happens to be the currency of the game) are slow moving hostile robotic threats found aboard derelict ships. They can be identified by subtle radio sound cues, or by a purple cone of light emitted from its front.
While they are possibly the least dangerous of threats, the player should be extremely careful. Should the player run into the drone, the player can successfully run from this threat or use weapons to dispatch it. The drones ability to detect the player is limited to the purple cone of vision in front of it.
Should the player kill the drone, it will drop 1 - 3. This drone can be destroyed easily by use of the turret upgrade and will die before it can retaliate. If you cannot kill it, it will always investigate rooms beyond open doorways, allowing you to trap it.
This threat can see through your stealth if it comes into contact with your drone.
This threat is the only one immune to lure and sonic, however, it is also the only one to attack sensors.
There seems to be a different type of security drone that can also shoot. Beware!
They can detect Stealth if you stand for too long too close to them and in their cone of vision.
Security drones can be destroyed by radiation.
Using Stealth after being caught by the drone (assuming that it was already active when the player was caught) seems to sometimes fool the security drone, giving the player enough time to flee.