Ship-board drone systems are likely to be the standard deterrent here. A small swarm of these things capable of sounding an alarm and launching a flare over the

Ship-board drone systems are likely to be the standard deterrent here. A small swarm of these things capable of sounding an alarm and launching a flare over the detected craft would give you a lot more time to prepare your defenses. These things show up on thermal imaging quite well, so finding them is not the problem. It's having systems that constantly scan and can alert reliably in the case of a problem with sufficient warning time that's tricky.