You can add a reCAPTCHA box to your form as an extra verification step to establish that a user is human.
1. On your campaign, go to the Creatives tab, select Forms and click Edit.
2. Click the Add Field button.
3. In the new field, click the dropdown under Type and select Recaptcha.
You can enable/disable the field at any time by ticking/unticking the Enabled box.
4. Click Save. The reCAPTCHA field will now appear on the form.