[rl3]

Most RTS games are simulations, so the client has to have the enemy unit positions in order to conduct its local simulation. In this case the best defense against map hacks (assuming it's closed source) is frequently updating the game, and messing around with the underlying unit data structures or systems each time there's an update. A map hack isn't very effective if it breaks every week or two on a regular basis, requiring more reverse engineering effort each time.

One notable exception to the local simulation model is Planetary Annihilation, which uses a traditional client/sever model as far as I'm aware.

[mohaine]

Changing the games doesn't really help unless you also change the network protocol as a lot of hacks just inspect the network data steams. This makes it harder to check for at runtime and it is harder to change the network protocols since changes break everybody on the old version.

I think quake cheats got to the point a cheat server would MITM the game and shoot automatically and or auto-aim shots for the user.