Entries Tagged "impersonation"

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Social Engineering and the IRS

Social engineering is still very effective:

More than one-third of Internal Revenue Service (IRS) employees and managers
who were contacted by Treasury Department inspectors posing as computer technicians provided their computer login and changed their password, a government report said Wednesday.

This is a problem that two-factor authentication would significantly mitigate.

Posted on March 22, 2005 at 9:54 AMView Comments

The Failure of Two-Factor Authentication

Two-factor authentication isn’t our savior. It won’t defend against phishing. It’s not going to prevent identity theft. It’s not going to secure online accounts from fraudulent transactions. It solves the security problems we had ten years ago, not the security problems we have today.

The problem with passwords is that they’re too easy to lose control of. People give them to other people. People write them down, and other people read them. People send them in e-mail, and that e-mail is intercepted. People use them to log into remote servers, and their communications are eavesdropped on. They’re also easy to guess. And once any of that happens, the password no longer works as an authentication token because you can’t be sure who is typing that password in.

Two-factor authentication mitigates this problem. If your password includes a number that changes every minute, or a unique reply to a random challenge, then it’s harder for someone else to intercept. You can’t write down the ever-changing part. An intercepted password won’t be good the next time it’s needed. And a two-factor password is harder to guess. Sure, someone can always give his password and token to his secretary, but no solution is foolproof.

These tokens have been around for at least two decades, but it’s only recently that they have gotten mass-market attention. AOL is rolling them out. Some banks are issuing them to customers, and even more are talking about doing it. It seems that corporations are finally waking up to the fact that passwords don’t provide adequate security, and are hoping that two-factor authentication will fix their problems.

Unfortunately, the nature of attacks has changed over those two decades. Back then, the threats were all passive: eavesdropping and offline password guessing. Today, the threats are more active: phishing and Trojan horses.

Here are two new active attacks we’re starting to see:

  • Man-in-the-Middle attack. An attacker puts up a fake bank website and entices user to that website. User types in his password, and the attacker in turn uses it to access the bank’s real website. Done right, the user will never realize that he isn’t at the bank’s website. Then the attacker either disconnects the user and makes any fraudulent transactions he wants, or passes along the user’s banking transactions while making his own transactions at the same time.

  • Trojan attack. Attacker gets Trojan installed on user’s computer. When user logs into his bank’s website, the attacker piggybacks on that session via the Trojan to make any fraudulent transaction he wants.

See how two-factor authentication doesn’t solve anything? In the first case, the attacker can pass the ever-changing part of the password to the bank along with the never-changing part. And in the second case, the attacker is relying on the user to log in.

The real threat is fraud due to impersonation, and the tactics of impersonation will change in response to the defenses. Two-factor authentication will force criminals to modify their tactics, that’s all.

Recently I’ve seen examples of two-factor authentication using two different communications paths: call it “two-channel authentication.” One bank sends a challenge to the user’s cell phone via SMS and expects a reply via SMS. If you assume that all your customers have cell phones, then this results in a two-factor authentication process without extra hardware. And even better, the second authentication piece goes over a different communications channel than the first; eavesdropping is much, much harder.

But in this new world of active attacks, no one cares. An attacker using a man-in-the-middle attack is happy to have the user deal with the SMS portion of the log-in, since he can’t do it himself. And a Trojan attacker doesn’t care, because he’s relying on the user to log in anyway.

Two-factor authentication is not useless. It works for local login, and it works within some corporate networks. But it won’t work for remote authentication over the Internet. I predict that banks and other financial institutions will spend millions outfitting their users with two-factor authentication tokens. Early adopters of this technology may very well experience a significant drop in fraud for a while as attackers move to easier targets, but in the end there will be a negligible drop in the amount of fraud and identity theft.

This essay will appear in the April issue of Communications of the ACM.

Posted on March 15, 2005 at 7:54 AMView Comments

Fixing Unicode

The Unicode community is working on fixing the security vulnerabilities I talked about here and here. They have a draft technical report that they’re looking for comments on. A solution to these security problems will take some concerted efforts, since there are many different kinds of issues involved. (In some ways, the “paypal.com” hack is one of the simpler cases.)

Posted on March 13, 2005 at 9:31 AMView Comments

Unicode URL Hack

A long time ago I wrote about the security risks of Unicode. This is an example of the problem.

Here’s a demo: it’s a Web page that appears to be www.paypal.com but is not PayPal. Everything from the address bar to the hover-over status on the link says www.paypal.com.

It works by substituting a Unicode character for the second “a” in PayPal. That Unicode character happens to look like an English “a,” but it’s not an “a.” The attack works even under SSL.

Here’s the source code of the link: http://www.p&amp#1072;ypal.com/

Secuna has some information on how to fix this vulnerability. So does BoingBoing.

Posted on February 16, 2005 at 9:17 AMView Comments

Flying on Someone Else's Airline Ticket

Slate has published a method for anyone to fly on anyone else’s ticket.

I wrote about this exact vulnerability a year and a half ago.

The vulnerability is obvious, but the general concepts are subtle. There are three things to authenticate: the identity of the traveler, the boarding pass, and the computer record. Think of them as three points on the triangle. Under the current system, the boarding pass is compared to the traveler’s identity document, and then the boarding pass is compared with the computer record. But because the identity document is never compared with the computer record—the third leg of the triangle—it’s possible to create two different boarding passes and have no one notice. That’s why the attack works.

Posted on February 8, 2005 at 9:11 AMView Comments

Canadian Airport Security Loses Uniforms

From CBC News:

1,127 uniform items belonging to Canadian airport screeners were lost or stolen in a nine-month period.

I’m not sure if this is an interesting story or not. We know that a uniform isn’t necessarily a reliable authentication tool, yet we use them anyway.

Losing 1,127 uniforms is bad, because they can be used to impersonate officials. But even if the 1,127 uniforms are found, they can be faked. Can you tell the difference between a legitimate uniform and a decent fake? I can’t.

The real story is the informal nature of most of our real-world authentication systems, and how they can be exploited.

I wrote about this in Beyond Fear (page 199):

Many authentication systems are even more informal. When someone knocks on your door wearing an electric company uniform, you assume she’s there to read the meter. Similarly with deliverymen, service workers, and parking lot attendants. When I return my rental car, I don’t think twice about giving the keys to someone wearing the correct color uniform. And how often do people inspect a police officer’s badge? The potential for intimidation makes this security system even less effective.

Uniforms are easy to fake. In the wee hours of the morning on 18 March 1990, two men entered the Isabella Stuart Gardner Museum in Boston disguised as policemen. They duped the guards, tied them up, and proceeded to steal a dozen paintings by Rembrandt, Vermeer, Manet, and Degas, valued at $300 million. (Thirteen years later, the crime is still unsolved and the art is still missing.) During the Battle of the Bulge in World War II, groups of German commandos operated behind American lines. Dressed as American troops, they tried to deliver false orders to units in an effort to disrupt American plans. Hannibal used the same trick—to greater success—dressing up soldiers who were fluent in Latin in the uniforms of Roman officials and using them to open city gates.

Spies actually take advantage of this authentication problem when recruiting agents. They sometimes recruit a spy by pretending to be working for some third country. For example, a Russian agent working in the U.S. might not be able to convince an American to spy for Russia, but he can pretend to be working for France and might be able to convince the person to spy for that country. This is called “false flag recruitment.” How’s the recruit going to authenticate the nationality of the person he’s spying for?

There’s some fascinating psychology involved in this story. We all authenticate using visual cues, and official uniforms are a big part of that. (When a policeman, or an employee from the local electric company, comes to your door and asks to come in, how to you authenticate him? His uniform and his badge or ID.)

Posted on December 29, 2004 at 8:37 AMView Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.