What is Two Factor Authentication?

Two factor authentication, or the snappy acronym 2FA, is something that you’re going to be hearing a lot about over the next year or so, both for use by ESP employees (in an attempt to reduce the risks of data theft) and by ESP customers (attempting to reduce the chance of an account being misused to send spam). What is Authentication?
In computer security terms authentication is proving who you are – when you enter a username and a password to access your email account you’re authenticating yourself to the system using a password that only you know.
Authentication (“who you are”) is the most visible part of computer access control, but it’s usually combined with two other A’s – authorization (“what you are allowed to do”) and accounting (“who did what”) to form an access control system.
And what are the two factors?
Two factor authentication means using two independent sources of evidence to demonstrate who you are. The idea behind it is that it means an attacker need to steal two quite different bits of information, with different weaknesses and attack vectors, in order to gain access. This makes the attack scenario much more complex and difficult for an attacker to carry out.
It’s important that the different factors are independent – requiring two passwords doesn’t count as 2FA, as an attack that can get the first password can just as easily get the second password. Generally 2FA requires the user to demonstrate their identity via two out of three broad ways:

  1. Something the user knows – a password or a PIN
  2. Something the user has – a key, an ID card, a phone number, a digital certificate or a physical token
  3. Something the user is – such as a fingerprint

An everyday example of 2FA is using a cash machine or ATM. You insert your ATM card (something you have) and enter your PIN (something you know) to get access to your bank account. An attacker would have to both steal or copy your card and know your PIN to access your account. While a crooked waiter might be able to copy your card and someone could look over your shoulder to see your PIN, it’s much more difficult for an attacker to get both.
Most deployed 2FA systems work in much the same way. They require you to enter a password you know, and then to demonstrate that you have something in your possession – by having your computer present a digital certificate, or having you enter a number from a security token like those pictured above, or respond to an SMS message.
Security problems solved, then?
I’ll look at that tomorrow.
(Spoiler: No)

Related Posts

Phishing protection

Last week Return Path announced a new service: Domain Assurance. This service allows companies who send only authenticated email to protect their brand from phishing attacks. Participating ISPs will reject unauthenticated email from domains participating in this program.

Read More

Authentication and phishing

Yahoo announced today that they are releasing the Yahoo! Mail Anti-Phishing Platform (YMAP) that will help protect their users from phishing. They have a similar project in place for eBay and PayPal mail, but this will extend to a broader range of companies.

Read More

Clicktracking link abuse

If you use redirection links in the emails you send out, where a click on the link goes to your server – so you can record that someone clicked – before redirecting to the real destination, then you’ve probably already thought about how they can be abused.
Redirection links are simple in concept – you include a link that points to your webserver in email that you send out, then when recipients click on it they end up at your webserver. Instead of displaying a page, though, your webserver sends what’s called a “302 redirect” to send the recipients web browser on to the real destination. How does your webserver know where to redirect to? There are several different ways, with different tradeoffs:

Read More