With last year’s Call of Duty: Modern Warfare, Activision rolled out an all-in-one Activision account that players can use whcih was benefical for crossplay. It made it easier to add friends, see who’s online playing Modern Warfare and/or Warzone and the like. Given how rampant account stealing is nowadays, the company has wisely rolled out the Activision account 2FA (two-factor authentication)!
For those not familiar with 2FA, it secures accounts tied to it, as it’ll send a text message with a PIN code in order for the user to login. This means that even if someone somehow guesses your password, they still won’t be able to log in to your account unless they have access to your mobile phone too.
Note that while you might see that it Google authentication app, you don’t need to use it and you can use authy instead. Instructions on that per Reddit: