[carlmr]

I was also wondering what is exactly the illegal part in a service to check cards, except for who's using it for what.

I'm maybe naïve to this, because I don't know how the check is being performed.

[toast0]

Typically by making a small (fradulent) purchase at an innocent merchant and seeing if it works.

This is illegal because of the fraud. It harms the merchant in all sorts of ways, and also the cardholders and issuers.

[sfe22]

What if they refund it immediately? Maybe that is what they did, to avoid detection. Anyone knows more about this?

[toast0]

If the checker is running the cards on their own merchant account and refunding immediately? Or doing auth, but not capture?

That's going to be in records of accounts that eventually report compromises, and get figured our pretty quick, I'd imagine.

[carlmr]

Isn't that what a lot of legit companies do?