With the number of hackers and system breaches that are mentioned in the news lately site security is no laughing matter. One of the best options to come to most email systems has been 2 step authentication like Gmail introduced. Thanks to Sam Battat that same 2-factor authentication provided by Google can now be used on your Moodle site to increase security for student accounts.
A2FA (Another 2-Factor Auth) creates a two factor authentication process for students using the Google Authentication app (which can be downloaded to a phone). During the login process students simply enter in their code which expires every 60 seconds.
Check it out at https://moodle.org/plugins/view.php?plugin=auth_a2fa
The addon also requires a QR code plugin which is added to the user profile and used to sync 2-factor authentication which is also available from the addon database: https://moodle.org/plugins/view.php?plugin=profilefield_afaqr.