Amazon:

Amazon’s Two-Step Verification adds an additional layer of security to your account. Instead of simply entering your password, Two-Step Verification requires you to enter a unique security code in addition to your password during sign in.

You’ll enter your sign in information like you normally would, but then you’ll be prompted to enter a security code. You can receive this security code in a variety of ways depending on the option you select during sign up, including text message, voice call, or authenticator app.

Some folks will think this kind of security is inconvenient. But any time I give a company my credit card info and I want that info stored on their site, I feel more comfortable if the site offers this additional level of security.