I have added IP's to the blacklist section in the past. Lately if I add an extra IP I get the following error message:
You don't have permission to access /wp-admin/admin.php on this server
Additionally a 403 error was encountered while trying to use an error document to handle the request.
I just stopped adding IP's but get a few failed login's each day that the plugin catches.
Today I tried to install the brute force option and got the same message. I just get an earlier backup reinstalled and I am back in operation.