Survival games is a great idea, but unfortunately many players will use modified (or "Hacked") clients, which allow them to do things that would be normally impossible. For example, climbing a wall as if it was a ladder (or as if you were a spider), reaching further than normally possible, automatically hitting players and monsters within a certain range and the list goes on.

Fortunately for you and all of us who do play fairly, these few people will get banner sooner or later because there are plugins to detect this. If you catch anyone "Hacking", take a screenshot and report it to a moderator because in the long run, it is worth it.