Google Authenticator

Google Authenticator is a software-based authenticator used for secure account management. The software is developed at Google and is a two-step verification services, using a time-based one-time password algorithm. When using Google Authenticator to secure an online account or service, your risk of getting compromised is drastically reduced. When an account is protected with Google Authenticator an attacker must not only know your original password but also has access to any of your Google Authenticator enabled devices to gain access to your account.