WikiServer - Securing the Wiki
There are a number of settings and tweaks that can save you grief while maintaining your wiki.
Contents
Item #1 try hard not to be bored during the install...
Item #2 disallow edits
by anyone who is not logged in with a valid account. This is done by choosing "Authorised editors only" as the User rights profile.
The default, Open wiki, is pretty much asking for spam & chaos...
Item #3 account creation control.
A good starting point to manage account creation (albeit manually...) is to add $wgGroupPermissions['*']['createaccount'] = false;
to your LocalSettings.php (which is hiding out in /etc/var/html/wiki
on a stock-standard install)
Using this method, it takes an Administrator to actually create a new account.
Further thoughts
There are a large number of further items in the documentation, including plugins & add-ons to enhance security.
Thes 3 items listed here are a good starting point tho.