If you wish to prevent automated signups you need to make sure you set up reCAPTCHA for any of your custom domains. MyOrderDesk currently supports reCAPTCHA v2. You need to generate a Site Key and Secret Key using Google's Admin page: https://www.google.com/recaptcha/admin
Use this link to Register a new site: https://www.google.com/recaptcha/admin/create
Make sure to choose reCAPTCHA v2 and enter your custom domains in the Domains section.
Label: Use a label that will make it easy for you to identify the site in the future.
reCAPTCHA type: Select reCAPTCHA v2 and "I'm not a robot" Checkbox
Domains: Add all of the custom domains you would like to use.
Once set up you will want to copy your Site Key and Secret Key to your MyOrderDesk website in the Site Settings > Options > Sign Up & Security.
Make sure to test your sign up page for all of your custom URLs to ensure there are no issues.
To complete the process, you will next need to go to the Site Settings > Options > Sign Up & Security page and enter in the Keys. You will not be able to enter reCaptcha details until you have your custom domains set up.