Enchantment hack?

My server has recently got these group of people who have these enchantment hacks pretty much gives the player legit uber enchantments but hides it as a normal legit enchanted item. I have no knowledge of this hack. If anyone could spill some knowledge on how to stop it or anything about it would be nice thank you.

Fun fact: Kill aura + sharpness (anything above 1) + 2-5 seconds of direct combat (depending on armor) = death.

We grabbed a normal sharpness 3 sword and the hacked sharpness 3 sword. The hacked one did more damage.