Explain Two factor Authentication in windows server 2012

In general the two factor authentication is exactly as what Mr. Yassine Esserkassi has explained in his answer.2Factor Authentication (2FA) is like using something like smart cards, one-time passwords or anyother method along with the usual username and password authentication. But in windows servers this could also be useful when using Remote Desktop (RD) WebAccess, where you share your whole desktop on internet. You can achieve these feature using RD webaccess servers along with RD Gateway. The below will take you through much more details regarding this.  

http://technet.microsoft.com/en-us/library/cc770330.aspx

http://microsoftplatform.blogspot.in/2011/06/what-new-features-or-improvements-would.html

http://microsoftplatform.blogspot.com/2011/05/force-use-of-rd-webaccess-block-direct.html

I am agree with all of them about Two factor authentication. The purpose of this Authnetication is to provide hard core security to your credentials. Now a days Using only username and passwords for authentication is no more a secured way to protect systems or services. we need some thing more than username and passwords like biometric readings, smart cards, one time passwords-OTP through SMS or email. All these aims to prevent unauthorized access.

Authentication is a method of access control to a system. A user can pass the authentication by providing the authentication factor(s) such as the password (only the user knows it) (knowledge factor) or an ID (only the user has it) (possession factor) or a fingerprint (only the user has it) (inherence factor). All these factors are used to apply security in access control.  

Two factor authentication helps protect your account by making it more difficult for a hacker to sign in, even if they've somehow learned your password. The second factor prompts you to enter a security code to sign in. This security code can be sent to your phone or your alternate email address, or you can obtain one through an authenticator app on your smartphone or any other3rd party security method such as smartcards, usb dongles etc.

Since the evolution of database hacking & intrusion techniques, the simple authentication has become vulnerable. The two factor authentication has been introduced as a strong and secure way to authentify a authorized user, because it adds another element of authentication to your simple authentication method. It's based not only on informations that you should know (like a username/password), but also, on an element that you should have, for example, a smartphone, a card, etc. Now, the two-factor authentication requires you to provide two elements of authentication instead of one to prove who you really are. A simple example of this technique in our everyday life is the credit card, in order to access your bank account, you need to use something that you have (your credit card), and something that you know (your pin code). Even if it's stolen, the thief cannot access you bank account. This way, it's more secure, and simple to use. Hope my explanation helps. 

Two-factor Authentication is a method of strong authentication requiring two different forms of identification instead of the traditional single password.

Two-factor authentication solves a lot of problems. Some of them include:

• Phishing attacks. With two-factor authentication, phishers could not steal user names and passwords and gain access to private information; since they cannot steal the second factor, the user name and password ends up being worthless to the attacker later on
• Identity theft. Much of what we see in the area of identity theft is moving online; identity thieves might be able to steal or guess private information about a person, such as a pet’s name, user name, password, or date of birth, but they won’t be able to steal the second factor, making it impossible for them to impersonate the victim
• Complex and multiple passwords. Users come up with creative means to subvert complex passwords, and become even more enraged by having to remember complex passwords for multiple systems; two-factor authentication removes this onus from the user, so that the only things required are a relatively simple password and a second factor

Given all of the advantages of two-factor authentication, you have to wonder why it’s not universally deployed on all networks, regardless of size. There are several reasons why this is the case, the two major ones being:

• Cost - Most two-factor authentication systems are extraordinarily expensive, leading them to be used only by large enterprises with deep pockets
• Complexity - Most two-factor authentication systems are complex to set up and configure, some of them requiring dedicated server resources and their own authentication repositories to make them work