[plextoria]

This intrigued me and I topped up an account. Is there no password? Anyone could "steal" my account number and kick me out?

[BrunoBernardino]

There is no password, just like Mullvad. You should "protect" your account number like you would a password, but also, you can just discard it and change to another one in a month, for example.

[plextoria]

Thanks for your answer! Makes me curious how do you defend against people simply bruteforcing or guessing the account numbers.

[BrunoBernardino]

Rate limiting when it's invalid (and high entropy to generate new ones)! It's in the FAQ :)