You can read more about securing your site in the <a href="https://drupal.org/security/secure-configuration">drupal.org handbooks</a> and on <a href="https://crackingdrupal.com">CrackingDrupal.com</a>. There are also additional modules you can install to secure or protect your site. Be aware, though, that the more modules you have running on your site, the greater (usually) attack area you expose.