So adding the line above is making all my sites more susceptible to a compromise? Can you explain how, please? It's just a line or two of similar coding so the email sent me the admin (me) has the IP in case I want to ban. Simple script, chmod protected, no backdoors.
I try not to ban each IP as it fills .htaccess and puts a load on the server. I just watch the log for a few days. If I see that IP repeatedly trying to login on one name, I approve as Spectator. They can visit but not post. Sometimes I ban the IP if they registered multiple nicks.
Get the plugin I suggested. Also, I, too, don't have time to deal with this as I'm online two hours per day. Weekly I check registrations. I have to manually approve each person so signing up doesn't give access -- I do. I modified the signup email saying it takes up to seven days for approval. I keep that on my side and FTP it to each new site.
Lastly, I lost memory but I used to go into a DOS window, type the IP with something and the port, to see if it is open. If so I used to ban on my own server. You may want to do that to an IP and if not open, don't worry about a ban.