If your nonprofit uses Authorize.net as your payment gateway you'll need to configure it to detect and prevent fraud and alert you to suspicious transactions. Authorize.net provides a product called the Advanced Fraud Detection Suite for this purpose.
The Advanced Fraud Detection Suite allows you to set rules for when you will accept or reject credit card payments, when a payment is potentially fraudulent, and when it should be considered legitimate.
How to configure the Advanced Fraud Detection Suite
Each of these 4 steps is reviewed in detail in the video below.
Make sure your Authorize.net account has the Advanced Fraud Detection Suite (AFDS) installed. If not contact Authorize.net support to have that installed.
Configure the AFDS to monitor for credit card fraud.
Set up email alerts to alert your organization of all suspicious transactions taking place. Appoint yourself or a specific member of your staff to take responsibility for these alerts and what action you should take if they occur.
Set up an online response for donors to see when their online donation is denied due to a fraud setting.