By default, the MailChimp for WordPress plugin uses various techniques to prevent spam sign-ups. Unfortunately, some spam-bots are smart enough to get through and more actions might be required. Bots are getting smarter everyday and sometimes even target your sites in a specific way.
If you’re suffering from spam sign-ups, the following methods will help you reduce and maybe even eliminate them.
Enable double opt-in
Double opt-in is a method where your subscriber will receive a confirmation email for your list. Most bots will not be able to get through to your list when this option is set to yes.
You can find this setting when editing your form; scroll down to find MailChimp Settings and set the double opt-in to yes.
Enabling should prevent most of the spam sign-ups already. If not, continue to the methods described below.
Install the WP Bruiser plugin.
The WP Bruiser plugin (formerly called Goodbye Captcha) uses a highly effective anti-spam technique which does not even require your visitors to fill an additional field. We’ve integrated this plugin with our so they work together seamlessly. If you’re having issues with spam sign-ups, this is a plugin we highly recommend!
Add Google reCAPTCHA to your forms
Another option to prevent bots from filling out your form is to rely on Google reCAPTCHA v3. This method works by monitoring your form submissions over time and finding a distinction between human visitors and bot visitors. This means that the longer you have reCAPTCHA enabled, the more bullet-proof this anti-spam solution will become.
Mailchimp for WordPress ships with built-in integration for Google reCAPTCHA. We have an article describing how to add Google reCAPTCHA to your sign-up forms.