reCAPTCHA is a service that protects your site from spam and abuse. It uses advanced risk analysis techniques to tell humans and bots apart.
To prevent the fake donations from being made, go to Main menu > Organization; Scroll to the bottom of page and “Enable the reCaptcha” feature, then click update to save your changes.
Note: disabling the reCaptcha security feature, makes your donation pages and campaigns vulnerable to fake $1 or $5 donations. In which case, monitor your account for the fake donations and re-enable reCaptcha if/when you see them".