Attack people when they are online.
This is just a fast idea how to stop people who are chea-ting by being online by using machines and all that kind of stuff..
You should be able to get attacked when you are online! How this could work is when you are online and someone attacks you then you wont be able to see it but when you log out and log in Again then you can see that he have attacked you. If he destroys your base and you wil get a shield you wil lstill get your shield and people can no longer attack you ofcourse.