Some robot is trying to figure out the username and password for my admin area.

I'm getting several login attempts in the admin area of my site. Some robot is trying to figure out the username and password for my admin area. I already set up WP Defender to block the user and the IP number, but this robot changes IP every time I try again.

I can not change the URL because my site has integration with other systems. If I change the URL it will give a problem with the other systems.

I have also added Google Captcha ...

Please, help me