So restrict radar reporting (under-dar) to squad and mission. That eliminates the majority and the random.
I don't know how many NOE's I've spoofed just being in the right place. Usually because I refuse to use front line fields. Having guys that are "lifters" along also goof the mission up. I don't know if its intentional or not, but I had a guy that just refused to stay low. I've also had the "friendlies" shadow the NOE mission, I assume to help. No amount of communication seemed to work. Was this guy a spy? or was he just new and didn't know any better? I have no idea, but he was annoying.
IP addresses wouldn't work well, I personally own 8 IPs for my own networking purposes. They are all static. Others have multiples assigned dynamically from their ISPs because they have multiple computers.
Unless the guy is internet sharing or actually using the same computer to run multiple instances of AH you won't get the same IP.
Spying happens, been happening for 7000-years of recorded history.