the black security camera looking things

occasionally when in building i see a black dome shaped thing on the ceiling with a target symbol that looks like the mission target symbol but with purple. what are these?
in case nobody knows what im talking about i will screen shot it next time

Thats a security camera, when you enter a room if you haven't shut of the security system with the spy ability all the enemies in the area will rush into that room.

Yeah.  In order to disable those cameras you have to disable the security devices with the skill... disable security devices.  They look like a giant breaker (electricity breaker).