It didn’t take me forever to find this, but I felt it was simple enough that it bore re-posting.  If you’ve ever wanted to disable anonymous editing of articles in a mediawiki-based wiki (the ones that look & feel like wikipedia…) there’s a simple one-line fix:

In your LocalSettings.php file, add this to the bottom: #Disable Anonymous Editing $wgGroupPermissions['*']['edit'] = false;

It should be noted that this fix is for MediaWiki 1.5 and later. If you want some ideas on additional things that you can do with MediaWiki security, check out the MediaWiki Manual.