eBay can be set up to send you a PIN confirmation email each time you log into a new device it doesn’t recognise. It’s not foolproof, and arguably we have far better systems for multi-factor auth, but it’s a start.
This is what eBay sends:
Subject: Here’s the eBay PIN you requested
Confirm your identity: Here’s your PIN
Here’s the eBay PIN you requested
Here is the PIN you’ll need to finish confirming your identity on eBay. It’s just one more step, and then you’ll be on your way.
Your PIN is: HERES-YOUR-PIN [ed: okay, I made that up]
My favourite was them saying it’s just one more step, as if reassuring me after saying I’d be getting a PIN four times. Then another time. But are they sure I’m getting a PIN?