A good way to add extra security to your phpBB forum is to create an added layer of password protection over vital areas like the Administration Control Panel. If the server hosting your site uses Apache, as most servers do, you can accomplish this with .htaccess and .htpasswd files. These are special files that are used to change the server configuration to accomplish many tasks, including password protection. You can use this generator to create these files for your site.
We recommend that you do not use a username or password that you have ever used for anything else, for added security.