Your Facebook account can be protected with two-factor authentication (2FA). This means that you add an extra layer of security to your Facebook account. For the second step, you can use 4.6 - Nexus Personal Mobile, which is an application for online 2FA. Once set up, you sign in to Facebook with your password and a one-time password (OTP), sent to your mobile device.
Nexus Personal Mobile offers extra security compared to other mobile apps for online two-factor authentication, since you also authenticate your self in Personal Mobile with a PIN code or your fingerprint before you receive the OTP.