The Bad Words management page
This page allows you to manage the list of Bad Words. Their use will be forbidden on the site. If a query contains one of those words, it will result in a 403 error and it will optionally be logged in your Blocked Requests Log. You can use the standard Joomla! toolbar buttons to administer the list. All words are case insensitive, which means that they will be filtered no matter if they appear in lowercase, uppercase or mixed case in the request.
Some servers already include a server-side filter to avoid common spam words. If you receive an error —usually a 403 error or an error noting that you have an invalid request— while trying to save a word, do not panic. It's your server's filter kicking in. Just omit including the word you just tried to include, as it is already filtered very effectively by your server!