There is a decent anti-cheat plugin.
And I'm afraid that all the people who say "fix yur anti cheat" or "you need to make a better anti cheat for cubecraft" dont even have any idea how difficult it is.
Its a cat and mouse game between anti-cheat devs and cheat client devs that will keep going and is going for a long time already.
At this moment the cheat client devs are mostly one step ahead off the anti-cheat dev which is only Loony currently.
Also, next time I would suggest you to first take a loot at the threads that already exist before making a new one.
Because there are just tons of "Anti cheat" threads and its mostly about one thing; improving the anti cheat.