You can imagine doing surgery on the brains of insects or spiders to implant electronic devices and transmitters so that it becomes a drone and will transmit data. To gain intelligence on a target of interest one could release a large numbers of such spiders nearby and steer them to locations of interest.
"Feasible" parts (not that it has actually been done, but could be considered true if someone told the world he has).
- Connecting an electrode to an spider glanglia to force it to move where you want it to go.
Communications. The small size of the spider means that there is little place for an antenna. Emissions would be very short ranged unless you use LOTS of power (see next point).
Power. There is no battery technology that would provide a power source for the electronnics on the spiders for a decent (3 - 4 days) time range.
- You may direct the spider, but most probably you cannot "tune in" with the spider senses to know what the spider sees and or hears (even if you "connect" the right ganglia, the signal will be meaningless because the sensory organs are very different). You will need additional video and sound hardware tiny enough to fit in a spider. And power those up with the same battery as above.
Basically, short range of communications and battery life means that the spiders will only be useful if the ISIS HQ happens to be almost next door to you (and if that is the case, drones and troops on the ground would do a better job).
Ooh. Fun question.. And weirdly the answer is a...
Cyborg moths are a thing, as are cyborg cockroaches, so we know that we have the technology not just for control of the insects, but also for carrying sufficient power to contact a base station and adding in some small sensing capability (though the spiders aren't the ones doing the sensing). These drones could be used as one shot wonders, going in, gathering data, then using up their remaining power bursting a (reasonably stong) radio transmission back to wherever they came from before finding a nice dark corner (a behaviour already hardwired into most spiders) and curling up to die.
It's also worth noting that 'go into the light' and 'hide' can be effected using chemicals delivered into the spider, letting you offload a lot of processing to the spider while you passively listen for information.
This could be further enhanced by having a larger, more powerful spider 'nest' that serves both as a delivery vehicle and an intermediate data storage unit. The spiders are released, record information, are occasionally controlled via signals relayed through the nest (or if you want a passive system they record, die, and then the nest is picked up later for hard data-retrieval). If you include a solar recharge station in the nest you could even have the spider drones coming back to the nest for recharging (potentially via an inductive loop system in their underbellies).
The two biggest problems are robustness and stealth. Most spiders aren't as robust as moths or cockroaches, so mounting the hardware might prove to be an issue on any species small enough to not be noticed. Oh, and PCB's aren't exactly well camouflaged, so you'd have to work on that.
Other than that you've got a multitude of options. Enjoy your cyberentemology!