You can set IP addresses allowed to Login to your admin portal in Settings → Security Settings → Admin Area Allowed IPs.
If you'd like to go further, and block unwanted IP addresses on web-server level, you can do so by updating nginx config files.
How to IP-limit admin-area access on nginx
1. SSH to your HostBill Enterprise server as root:
2. Create file /etc/nginx/hostbill_phpfpm, add the following content to it:
3. Edit file:
3. Reload webserver's config