Think your ecommerce shop is fraud proof? Nope. You can't set up your store and not pay attention. Fraudsters are so clever these days...
One fraud plan uses purchase of gift certificates. They watch and wait a while. If their target didn't catch the charge up front, then the purchase doesn't trigger a fast charge back. Then they use the gift certificate and buy your products.
Once the credit card owner discovers the fraud, guess who gets to absorbe the loss? It's not the credit card company, folks, it's you!
ALWAYS pay attention to IP addresses on orders that look even the tiniest bit sketchy. The "buyer" may show an IP that's a VPN. Call the phone number and see it's a number that actually works (usually does not).
What's your sell pattern? If you see an unusal jump in orders for gift certificates, does it trigger a little bell in your head? Be smart.
Shopify has some excellent information on fraud prevention. If you're going to sell online, you can't know too much about ecommerce fraud.