I tried creating recently a new wiki, and even though I disallowed direct user creation (users would have to request to have an account) and edits from anonymous users, it was still overtaken by spam. The wiki was no longer even online. Looking at the database tables, it seems that a number of usernames have been created somehow, most of them start with "en>" or with "it>" and have a NULL value for the "actor_user" field. If I try using the rollbackEdit.php script with these usernames I get the error message "Invalid username". I'm not sure if that's because the username contains the ">" character, or if it's because "actor_user" is NULL. Any suggestion on how to go about cleaning up the mess? Since I had just started the wiki and had hardly any contents, I suppose I could just remove it completely and start all over again. I wonder how the usernames were able to be created if I disabled direct user creation?