Code Griefing: It is a form of griefing where a user gains access to code (especially world code) and abuses it to render the lobby useless, or almost unusable.
Classic Griefing: Abusing creative to hold explosive items, such as the "RPG," "Grenade Launcher," and "Moonstone Explosive."
Exploit Griefing: Uses exploits to lag or stall worlds lobby commands, so their framerate drops.
Extreme Griefing: Forces players, moderators, coders, co-owners, or owners to use any of the forms of griefing above.
How to Prevent It
Call one of the AGA agents for help.
Restrict access for more users, if that helps.
Put protective world code in the lobby, so it actively stops players from griefing.
Clearly investigate the players and what they are doing.