Adding these lines into LocalSettings.php will allow only logged in users to read/edit:
$wgGroupPermissions['*'    ]['read']            = false;
$wgGroupPermissions['*'    ]['edit']            = false;
$wgGroupPermissions['*'    ]['createpage']      = false;
$wgGroupPermissions['*'    ]['createtalk']      = false;Furthermore, adding the following will allow only sysop to create accounts:
$wgGroupPermissions['*'    ]['createaccount']   = false;
$wgGroupPermissions['sysop']['createaccount']   = true;
$wgWhitelistRead = array( "Main Page", "Special:Userlogin", "-", "MediaWiki:Monobook.css" );See http://ericsantiago.typepad.com/eric_santiago/mediawiki/index.html

