The standard security mechanisms you have seen before only require a simple username and password, which makes it increasingly easy for cyber criminals to gain access to confidential data, such as personal and financial details, either by hacking the password or by intercepting user credentials (emails, network sniffing, and such). This data can then be used to commit financial fraud and identity theft.

Two-factor authentication adds an extra layer of security since it requires not only a username and password, but also a two-factor code that only the user can provide (physical device, software-generated, and so on). This makes it much harder for potential intruders to gain access and thus helps to prevent identity and data theft.

All major websites provide two-factor authentication as an option, so let's add it to the Tic-Tac-Toe application as well.