If you already have BILLmanager, you need to protect it from bots. They consume much server resources and create numerous fake accounts in the database.
BILLmanager is integrated with reCAPTCHA from Google. This is a well-known scheme: a user must select the check box “I’m not a robot” on the sign up form. The system analyses his behavior and If it thinks he is not a human, he will be offered to pass through an image verification.
Now the billing system also supports Invisible reCAPTCHA which is not shown to a user. He doesn’t need to check the box, as the verification runs in the background. You can configure this option in BILLmanager → Global settings. For more information please refer to this article.
Invisible reCAPTCHA is available in BILLmanager 5 starting from version 5.173.0. It is not supported on the login form BILLmanager 6