I've already got active and passive detectors, active ones have three times the power and five times the cross-section contribution. (Obviously these numbers are temporary, I'll normalise properly as I get to the playtesting stage.) I'm also going to have a certain amount of player-choice stealthiness; since shutting down modules reduces their energy use, it also reduces ship cross-sections and makes them much more difficult to detect.

If you have sensor sharing between squads / fleet, jamming the sensors may be a useful countermeasure. I'm sure we are familiar with what jamming does so I won't go into it.