Minecraft wiki entry for Furniture, associated text: Griefer's trick: Add a TNT trap with a dropper and a wooden pressure plate hidden and a trapdoor to open the computer system and add a book to the dropper. You can use them as 'viruses' to wreck their computer. Add a button next to the dropper to turn it 'on'. Add a command block next to the pressure plate “hidden” and set the command to: /me ERROR! VIRUS ERROR!. When a player has turned 'on' their computer, the ERROR! alert will make the player think there is a virus and then the computer will explode!