There is no way to prevent people that use hacks (not hackers - it is a wrong term) from entering a game. Not even with a non cracked server. There are ways of making things less easy for them, and the most important one of those things is online staff. Reporting just leads to a lot of work because reports need to be reviewed. Direct action is more effective and has more effect on the hack users community. I have been playing on this server for 3 days now, and i spend a lot of time online. I barely see staff online. Maybe it is because it is vacation, but even then, with the number of staff that I see in the staff list, i'm surprised.
Maybe there is to much old staff that is not active anymore ?