Two-factor authentication (2FA)

Requiring a second proof of identity beyond the password, such as an SMS code, an authenticator app, or a hardware key.

Two-factor authentication adds a second, independent check to a login: something you know (password) plus something you have (a phone, an authenticator app, a hardware key). Even if the password leaks, the account holds.

SMS is the most common second factor and the weakest of the mainstream options, because phone numbers can be hijacked. For accounts created with a rented number, enable an authenticator app as the second factor so the account never depends on a number you no longer control.