Vandal

A vandal is an individual who edits a wiki with the sole intention of damaging it.

An effort needs to be made to understand vandals - they may not necessarily all be bored, unproductive individuals. For example, a user may disagree with a particular topic and lack the literary skills to make a reasoned case for carrying out any changes; alternatively they may think it's "fun" to make nonsensical comments.

Experience suggests that it's actually better to try and engage vandals as they frequently turn out to have wiki skills which could be used to improve the sites they attack.