Here you can control the banning of users. You can achieve this by banning either or both of a specific user or an individual or range of IP addresses or hostnames. These methods prevent a user from even reaching the index page of your board. To prevent a user from registering under a different username you can also specify a banned email address. Please note that banning an email address alone will not prevent that user from being able to log on or post to your board. You should use one of the first two methods to achieve this.
Please note that entering a range of IP addresses results in all the addresses between the start and end being added to the banlist. Attempts will be made to minimise the number of addresses added to the database by introducing wildcards automatically where appropriate. If you really must enter a range, try to keep it small or better yet state specific addresses.