This is my guide on vandalism (from the Crest of Xia Wikia):

Vandalism is the act of irritating and angering people on wikis through the use of destruction, construction, and social engineering. Popularized on Wikia by teams, vandalism has become a serious problem for admins and can bring drama into wikis.

Trolling, however, is different from vandalism, because afterwards vandals give their items back, and repair any damage they did.

Problems caused by vandals

Non-admin vandals

Type Description How to prevent
Destruction Self explanatory. Most vandals' goals are to destroy as much content as they can, so they can make pages unusable and destroyed. Protection has become useful on wikis, and they can protect pages to prevent this problem.
Creation Nearly as frequent as destruction, vandals often attempt to add spam, gibberish, and false information to pages and offensive information such as profanity, graffiti, or unnecessary edits to pages. This is the most common type of vandalism.
Edit Warring After another user reverts any damage they did, they revert the fix the other user did. The admins will have to revert any damage they did, ban the vandal, and protect the page.
Spamming Spamming is the act of typing large amounts of unwanted text on pages and comments. This can result in a lot of lag, which is more annoying than vandalism. Some JavaScript can limit the size of a page, or if able, admins or bots are able to revert any damage they did.
Page Move Vandalism What the vandal does is changes the page name to offensive, irrelevant, or disruptive names. Protect the page so only your staff can change or move pages.
Picture Vandalism This type of vandalism is different, what the vandal does is uploads/replaces images with shocking/disgusting content, or simply using an image that is disruptive. The only way to stop this is contact the VSTF and protect the image.
Template Vandalism This type of vandalism is basically modifying templates to make it look funny on a few pages. If there is a template you commonly use on your wiki, highly protect it to prevent this problem.
Vandalbot This type of vandalism is hard to commit, what the vandal does it sets up a bot script on their account to create loads of spam and vandalism. Only the VSTF can take care of vandalbots.
Sockpuppetry If able, vandals can create more accounts after they were banned to cause more trouble. This can be a nuisance because they evade their bans, return to the wiki, and continue their vandalism, and can make bans ineffective.  Sockpuppet accounts can be reported to the VSTF. The Wikia staff will close those accounts. Alternatively, you must make sure you tick the box "Prevent account creation" so this doesn't happen.

Admin/bureaucrat vandals

Type Description How to prevent
Theme Changing What the vandal does is breaks into the Theme Designer in the Admin Dashboard and changes the theme to whatever they desire. The only way to prevent this is if you have proper CSS installed to your theme.
CSS and JavaScript Changing Some smart vandals can sometimes break into the CSS and JavaScript pages and add spam, such as covering the entire page with a YouTube video, or putting strobes, which could affect the user's senses. This can be prevented if you have proper bots installed.
Hack Trolling This is one the hardest types of vandalism to commit and possibly the rarest. What happens basically is the vandal hacks the wiki and gains bureaucrat rights, bans the founders, co-founders, and admins (so the people who can ban other users can't), and removes their admin rights. Therefore the hacker takes over the wiki and becomes the new owner. The hacker then plasters the wiki with destructive content and destroys everything on the wiki. Admins must contact Wikia to reinstate their admins, revoke the hacker's rights (if any are present on the account), and ban the hacker's username. If an active bureaucrat is not available or is being abusive, the wiki may either need to be closed, the bureaucrat to lose it's status, and/or request adoption. Alternatively, this can be prevented if you have proper bots installed.

How to prevent vandalism on your wiki

While there is not much that can stop a determined vandal, there are ways for a wiki to reduce the risks of being vandalized. The following is a list of steps wiki owners can take to try to keep their wiki protected:

  • Protect the major/important pages on your wiki so only registered users and your staff can edit them.
  • Do not let your staff abuse their rights. Also, be cautious when choosing admin/bureaucrat rights for your staff. Once you promote a user to bureaucrat, the promotion will be permanent and only Wikia staff or the user themself can remove it.
    • If abuse happens in severe cases, it may be a good idea to be an only bureaucrat and admin.
  • Be careful what rights your staff wants to have.
  • Be aware where you advertise the wiki. While exposure means more members, vandals can find it easily.
  • Become familiar with what vandals are capable of doing. There are no hacks to gain admin/bureaucrat rights or delete the wiki.
  • You must ban users who vandalize the wiki. Depending on your wiki's rules, bans can be assigned for initial or repeated vandalism.