What you are experiencing is most likely what we call “donor spam.” This can happen for a wide variety of reasons. Let me give you some context and a broader picture of all the ways we address this.
1) Install or activate the free Akismet plugin ( https://www.ads-software.com/plugins/akismet/ ). Then go to “Donations > Settings > Advanced” and ensure that our Akismet SPAM protection is enabled there and save changes ( You have already done this )
2) If that still does not help, I would suggest you install and activate the forked version of the Stop signup plugin link: https://github.com/mathetos/Stop-Donor-Spam/archive/master.zip. This plugin is forked by Matt, our Head of Support to include the functionality to stop spam donors or donations along with spam signups.
3) Also increasing the minimum donation amount is a huge method of preventing these types of attacks. You can do this by going to any donations >> donation options >> Set the minimum amount to 25.
To enable only a logged-in user to donate go to any donation form >> Form display >> Set “Guest donations” to disabled and then set Registration to “Registration + Login”. This will require a user to log in or create an account for donation.
If the above does not help, we have a custom snippet that will help you to add re-captcha to your donation forms.
Here is the link to the custom snippet to add a ReCaptcha: https://github.com/WordImpress/Give-Snippet-Library/blob/master/form-customizations/implement-recaptcha.php
If you need any help in adding a custom snippet to your website, you can check this detailed doc here for more help: https://givewp.com/documentation/resources/adding-custom-functions-to-your-wordpress-website/
Please note that this code snippet is provided as an example of how you can extend Give with code. It’s up to you to implement and customize to your liking. We cannot provide support for custom code on your website, only the code that we create and distribute.
Thanks!