Griefer

Griefers are those type of people that fall into the category of Troll. It's a commonly known fact that they cause grief to the people they torment. These people are commonly seen destroying unprotected buildings at any time they want. This includes the builder being offline, AFK or just doing stuff.

Most of these people are usually stupid, claiming to be able to hack. But there has been also smart griefers which you will never see.

Oh, and you can get banned for griefing. Unless you have actually take hacking lessons, don't grief. B4 has no forgiveness whatsoever.

How to prevent griefers

 * While building, plan out how much area you are going to use. If you have no idea, too bad.
 * /house and follow instructions