A vandal is someone who damages the content of wiki by adding or deleting information in a deliberate attempt to disturb or spoil the collaborative work of others. It's a non-constructive pattern that goes further than trolling , since it can imply the transferring of ongoing polemics to the wiki without caring about its general purpose. Vandalism is more common in open wikis than intranets, because a vandal usually operates anonymously. However, registered users can also perpetrate vandalism fueled by negative feelings toward the organization, such as being disappointed with the content or upset about something happening within the organization.
The easiest vandal to detect is one who adds one or more external links. The benefit to the vandal is free advertising and perhaps a boost in search engine rankings. This type of vandal is found by checking for external links in recent changes to a wiki.
A more subtle and harder to detect type of vandal is the one who alters content either to be funny or cruel. Unless someone verifies every fact or claim in every page edit, this type of vandalism may lie undetected for months. Once an instance of subtle vandalism is detected, one should review any and all edits made by the offending user or IP address, as there are likely more instances of the same.
Most wiki platforms have an option to rollback to a previous version. This is the fastest way to undo vandalism.