Cisco Duo Two Factor Authentication is one of the newest solutions offered by Cisco Systems.
Duo protects access to the network with:

Multi-Factor Authentication (MFA) – Verifies the identity of all users with strong two-factor authentication.

Endpoint Visibility – Checks that your users’ devices meet your security standards before granting them access.

Adaptive Authentication & Policy Enforcement – Sets policies to grant or block access attempts by user or device, based on contextual factors.

Remote Access & Single Sign-On – Allows seamless and secure access to cloud and on-premises applications and servers for
all users, all devices and all applications.