Add Authy two-factor authentication to WordPress. Users opt in for an added level of security that relies on random codes from their mobile devices.
Enable the plugin, enter your Authy API keys, and your users can enable Authy on their accounts.
Once users configure Authy through their WordPress user profiles, any login attempts will require an Authy token in addition to the account username and password.
For users with mobile devices that don't support the Authy app, they can receive their tokens via SMS.
For convenience, especially in a network instance, API keys can be set in
Plugin development is found at https://github.com/ethitter/Authy-for-WP.