Yeah I know theres nothing to stop the attack as such, when I installed your mod it seemed to work for an hour or so with no errors in the logs but then the next morning it started again, but with different errors showing "user" verification errors that show it was still the bots attacking, IDK how you guys are gonna fix it but they seem very persistant and have been trying every day for nearly three months now and they seem to be getting worse looking at the amount of errors in the logs, 60 errors today alone has been the most yet.
There is no way to "fix" it short of arresting every botnet master and every client who pays them for services. That, or disconnecting your website from the Internet. Maybe even cleaning and properly securing every zombie under their control (nearly all running Windows) The first solution isn't really practical, nor is the second. The third wouldn't work too well either.
Your errors show that the fixes are at least working. They can't get past the "verification" part of the login form to which they are blindly posting (by posting, I mean the HTTP POST method).
Arantor's mod was developed to stop a very specific
feature of the attack. It will not try to detect and stop all attempts, nor should it. Doing so would see many valid users blocked.
If you want the error message to go away, contact the author of that
modification and ask that they update to stop spewing notices into the error log, or at least help you to turn off that portion for your site.