There IS a solution. But that is rather uh... Complex?
The A3 server needs to (If not already doing) make sure that there is NO alteration of packets being RECIEVED by the server. (100% of altered packets are sent only to the server, I mean, why would the server alter its own packets? lol). This is a very complicated thing to do, unfortunately.
Most new hackers just send a HUGE amount of packets to the server at one time, and this can be detected by the server (Eg - Memora giving 200 Mil exp?). But smarter hackers send the packets little by little, to arouse almost no suspicion. This takes time, but if done right, can mean disaster.
But cyber law means that any server side hacker can be arrested

.
As for protection from this, I can only think of one thing. Gameguard.
This is a software that is used in MANY online games (Maplestory, Gunbound, etc), which is extremely effective against this. As soon as it detects ANY .dll files being injected (This is essential to the hacker), it shuts down the game.
Gameguard CAN be bypassed, but this is rather difficult, and they update often. This is the only solution I can think of for now
