The most popular method currently for preventing spam on forms is reCaptcha. This is a system developed by Google that prevents bots from submitting data. If you've ever seen the "I'm not a robot" box or had to select traffic lights or bicycles from a series of images, then you've encountered a reCaptcha.
If you use a service like Sendinblue, GetResponse or Mailchimp, it is possible to insert a reCaptcha directly when creating the signup form.
If your service does not provide it, or for any reason you need a captcha for your form, you can use the WordPress plugin reCaptcha by BestWebSoft . Once installed, you can decide on which forms you want to use this spam prevention system. Here's how to set it up:
In the ReCaptcha > Settings section , choose the Captcha version to use (I recommend V3);
Generate API key with Google ReCaptcha to connect it to your site;
Enter the Site Key and Secret Key provided by Google;
Select all the forms you want to use reCaptcha on, choosing between the default belgium phone number list WordPress ones and those created by plugins you installed.
Honeypot
Another rather effective method is to insert a field inside the form which in jargon is called a “honeypot”.
A honeypot is a form field that is hidden, even simply by using a few lines of CSS, so that users visiting the website cannot see it. A very specific rule is set on this field: in order to send data, the field must remain empty.
However, bots can find it (it is not hidden for them) and, since they automatically fill in all the fields they find in the forms, they insert values into it, so sending is not allowed.
Check if your newsletter service offers this option in form generation, otherwise contact a developer to create a custom form.
This solution is useful if you already know which email addresses are spam , or at least the domain used, or the IP address of the spammer.
There are several newsletter services that allow you to create a blacklist from:
e-mail address;
email domain;
IP address;
part of the IP address;
IPv6 address.
When a subscription occurs from items in the blacklist, it is blocked.
To help you with this list, you can check with DomainChecker.org. On this site you can enter an email address, domain, or IP address and see if it has been added to a blacklist.