Entries Tagged "security questions"

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Second SHB Workshop Liveblogging (3)

The second session was about fraud. (These session subjects are only general. We tried to stick related people together, but there was the occasional oddball — and scheduling constraint — to deal with.)

Julie Downs, Carnegie Mellon University (suggested reading: Behavioral Response to Phishing Risk; Parents’ vaccination comprehension and decisions; The Psychology of Food Consumption), is a psychologist who studies how people make decisions, and talked about phishing. To determine how people respond to phishing attempts — what e-mails they open and when they click on links — she watched as people interacted with their e-mail. She found that most people’s strategies to deal with phishing attacks might have been effective 5-10 years ago, but are no longer sufficient now that phishers have adapted. She also found that educating people about phishing didn’t make them more effective at spotting phishing attempts, but made them more likely to be afraid of doing anything on line. She found this same overreaction among people who were recently the victims of phishing attacks, but again people were no better separating real e-mail from phishing attempts. What does make a difference is contextual understanding: how to parse a URL, how and why the scams happen, what SSL does and doesn’t do.

Jean Camp, Indiana University (suggested reading: Experimental Evaluation of Expert and Non-expert Computer Users’ Mental Models of Security Risks), studies people taking risks online. Four points: 1) “people create mental models from internal narratives about risk,” 2) “risk mitigating action is taken only if the risk is perceived as relevant,” 3) “contextualizing risk can show risks as relevant,” and 4) “narrative can increase desire and capacity to use security tools.” Stories matter: “people are willing to wash out their cat food cans and sweep up their sweet gum balls to be a good neighbor, but allow their computers to join zombie networks” because there’s a good story in the former and none in the latter. She presented two experiments to demonstrate this. One was a video experiment watching business majors try to install PGP. No one was successful: there was no narrative, and the mixed metaphor of physical and cryptographic “key” confused people.

Matt Blaze, University of Pennsylvania (his blog), talked about electronic voting machines and fraud. He related this anecdote about actual electronic voting machine vote fraud in Kentucky. In the question session, he speculated about the difficulty of having a security model that would have captured the problem, and how to know whether that model was complete enough.

Jeffrey Friedberg, Microsoft (suggested reading: Internet Fraud Battlefield; End to End Trust and the Trust User Experience; Testimony on “spyware”), discussed research at Microsoft around the Trust User Experience (TUX). He talked about the difficulty of verifying SSL certificates. Then he talked about how Microsoft added a “green bar” to signify trusted sites, and how people who learned to trust the green bar were fooled by “picture in picture attacks”: where a hostile site embedded a green-bar browser window in its page. Most people don’t understand that the information inside the browser window is arbitrary, but that the stuff around it is not. The user interface, user experience, mental models all matter. Designing and evaluating TUX is hard. From the questions: training doesn’t help much, because given a plausible story, people will do things counter to their training.

Stuart Schechter, Microsoft, presented this research on secret questions. Basically, secret questions don’t work. They’re easily guessable based on the most common answers; friends and relatives of people can easily predict unique answers; and people forget their answers. Even worse, the more memorable the question/answers are, the easier they are to guess. Having people write their own questions is no better: “What’s my blood type?” “How tall am I?”

Tyler Moore, Harvard University (suggested reading: The Consequences of Non-Cooperation in the Fight against Phishing; Information Security Economics — and Beyond), discussed his empirical studies on online crime and defense. Fraudsters are good at duping users, but they’re also effective at exploiting failures among IT professionals to perpetuate the infrastructure necessary to carry out these exploits on a large scale (hosting fake web pages, sending spam, laundering the profits via money mules, and so on). There is widespread refusal among the defenders to cooperate with each other, and attackers exploit these limitations. We are better at removing phishing websites than we are at defending against the money mules. Defenders tend to fix immediate problems, but not underlying problems.

In the discussion phase, there was a lot of talk about the relationships between websites, like banks, and users — and how that affects security for both good and bad. Jean Camp doesn’t want a relationship with her bank, because that unduly invests her in the bank. (Someone from the audience pointed out that, as a U.S. taxpayer, she is already invested in her bank.) Angela Sasse said that the correct metaphor is “rules of engagement,” rather than relationships.

Adam Shostack’s liveblogging. Ross Anderson’s liveblogging is in his blog post’s comments.

Matt Blaze is taping the sessions — except for the couple of presenters who would rather not be taped — I’ll post his links as soon as the files are online.

EDITED TO ADD (6/11): Audio of the session is here.

Posted on June 11, 2009 at 11:42 AMView Comments

Secret Questions

In 2004, I wrote about the prevalence of secret questions as backup passwords. The problem is that the answers to these “secret questions” are often much easier to guess than random passwords. Mother’s maiden name isn’t very secret. Name of first pet, name of favorite teacher: there are some common names. Favorite color: I could probably guess that in no more than five attempts.

The result is that the normal security protocol (passwords) falls back to a much less secure protocol (secret questions). And the security of the entire system suffers.

Here’s some actual research on the issue:

It’s no secret: Measuring the security and reliability of authentication via ‘secret’ questions

Abstract:

All four of the most popular webmail providers — AOL, Google, Microsoft, and Yahoo! — rely on personal questions as the secondary authentication secrets used to reset account passwords. The security of these questions has received limited formal scrutiny, almost all of which predates webmail. We ran a user study to measure the reliability and security of the questions used by all four webmail providers. We asked participants to answer these questions and then asked their acquaintances to guess their answers. Acquaintance with whom participants reported being unwilling to share their webmail passwords were able to guess 17% of their answers. Participants forgot 20% of their own answers within six months. What’s more, 13% of answers could be guessed within five attempts by guessing the most popular answers of other participants, though this weakness is partially attributable to the geographic homogeneity of our participant pool.

Posted on May 25, 2009 at 9:56 AMView Comments

Balancing Security and Usability in Authentication

Since January, the Conficker.B worm has been spreading like wildfire across the Internet: infecting the French Navy, hospitals in Sheffield, the court system in Houston, and millions of computers worldwide. One of the ways it spreads is by cracking administrator passwords on networks. Which leads to the important question: Why in the world are IT administrators still using easy-to-guess passwords?

Computer authentication systems have two basic requirements. They need to keep the bad guys from accessing your account, and they need to allow you to access your account. Both are important, and every authentication system is a balancing act between the two. Too little security, and the bad guys will get in too easily. But if the authentication system is too complicated, restrictive, or hard to use, you won’t be able to—or won’t bother to—use it.

Passwords are the most common authentication system, and a good place to start. They’re very easy to implement and use, which is why they’re so popular. But as computers have become faster, password guessing has become easier. Most people don’t choose passwords that are complicated enough to remain secure against modern password-guessing attacks. Conficker.B is even less clever; it just tries a list of about 200 common passwords.

To combat password guessing, many systems force users to choose harder-to-guess passwords—requiring minimum lengths, non alpha-numeric characters, etc.—and change their passwords more frequently. The first makes guessing harder, and the second makes a guessed password less valuable. This, of course, makes the system more annoying, so users respond by writing their passwords down and taping them to their monitors, or simply forgetting them more often. Smarter users write them down and put them in their wallets, or use a secure password database like Password Safe.

Users forgetting their passwords can be expensive—sysadmins or customer service reps have to field phone calls and reset passwords—so some systems include a backup authentication system: a secret question. The idea is that if you forget your password, you can authenticate yourself with some personal information that only you know. Your mother’s maiden name was traditional, but these days there are all sorts of secret questions: your favourite schoolteacher, favourite colour, street you grew up on, name of your first pet, and so on. This might make the system more usable, but it also makes it much less secure: answers can be easily guessable, and are often known by people close to you.

A common enhancement is a one-time password generator, like a SecurID token. This is a small device with a screen that displays a password that changes automatically once a minute. Adding this is called two-factor authentication, and is much more secure, because this token—”something you have”—is combined with a password—”something you know.” But it’s less usable, because the tokens have to be purchased and distributed to all users, and far too often it’s “something you lost or forgot.” And it costs money. Tokens are far more frequently used in corporate environments, but banks and some online gaming worlds have taken to using them—sometimes only as an option, because people don’t like them.

In most cases, how an authentication system works when a legitimate user tries to log on is much more important than how it works when an impostor tries to log on. No security system is perfect, and there is some level of fraud associated with any of these authentication methods. But the instances of fraud are rare compared to the number of times someone tries to log on legitimately. If a given authentication system let the bad guys in one in a hundred times, a bank could decide to live with the problem—or try to solve it in some other way. But if the same authentication system prevented legitimate customers from logging on even one in a thousand times, the number of complaints would be enormous and the system wouldn’t survive one week.

Balancing security and usability is hard, and many organizations get it wrong. But it’s also evolving; organizations needing to tighten their security continue to push more involved authentication methods, and more savvy Internet users are willing to accept them. And certainly IT administrators need to be leading that evolutionary change.

A version of this essay was originally published in The Guardian.

Posted on February 19, 2009 at 1:44 PMView Comments

Sarah Palin's E-Mail

People have been asking me to comment about Sarah Palin’s Yahoo e-mail account being hacked. I’ve already written about the security problems with “secret questions” back in 2005:

The point of all these questions is the same: a backup password. If you forget your password, the secret question can verify your identity so you can choose another password or have the site e-mail your current password to you. It’s a great idea from a customer service perspective — a user is less likely to forget his first pet’s name than some random password — but terrible for security. The answer to the secret question is much easier to guess than a good password, and the information is much more public. (I’ll bet the name of my family’s first pet is in some database somewhere.) And even worse, everybody seems to use the same series of secret questions.

The result is the normal security protocol (passwords) falls back to a much less secure protocol (secret questions). And the security of the entire system suffers.

EDITED TO ADD (9/25): Ed Felten on the issue.

Posted on September 24, 2008 at 4:01 PMView Comments

The Curse of the Secret Question

It’s happened to all of us: We sign up for some online account, choose a difficult-to-remember and hard-to-guess password, and are then presented with a “secret question” to answer. Twenty years ago, there was just one secret question: “What’s your mother’s maiden name?” Today, there are more: “What street did you grow up on?” “What’s the name of your first pet?” “What’s your favorite color?” And so on.

The point of all these questions is the same: a backup password. If you forget your password, the secret question can verify your identity so you can choose another password or have the site e-mail your current password to you. It’s a great idea from a customer service perspective — a user is less likely to forget his first pet’s name than some random password — but terrible for security. The answer to the secret question is much easier to guess than a good password, and the information is much more public. (I’ll bet the name of my family’s first pet is in some database somewhere.) And even worse, everybody seems to use the same series of secret questions.

The result is the normal security protocol (passwords) falls back to a much less secure protocol (secret questions). And the security of the entire system suffers.

What can one do? My usual technique is to type a completely random answer — I madly slap at my keyboard for a few seconds — and then forget about it. This ensures that some attacker can’t bypass my password and try to guess the answer to my secret question, but is pretty unpleasant if I forget my password. The one time this happened to me, I had to call the company to get my password and question reset. (Honestly, I don’t remember how I authenticated myself to the customer service rep at the other end of the phone line.)

Which is maybe what should have happened in the first place. I like to think that if I forget my password, it should be really hard to gain access to my account. I want it to be so hard that an attacker can’t possibly do it. I know this is a customer service issue, but it’s a security issue too. And if the password is controlling access to something important — like my bank account — then the bypass mechanism should be harder, not easier.

Passwords have reached the end of their useful life. Today, they only work for low-security applications. The secret question is just one manifestation of that fact.

This essay originally appeared on Computerworld.

Posted on February 11, 2005 at 8:00 AMView Comments

Sidebar photo of Bruce Schneier by Joe MacInnis.