Schneier on Security: Fun with Secret Questions

http://www.schneier.com/blog/archives/2010/04/fun_with_secret.html

by kibwen • 14 years ago

60 19 14 years ago

schneier.com

tingley• 14 years ago

When I'm allowed to pick the question, I invariably pick "Which is it?", and the answer is a series of random words.

Now you know, identity thieves.

mike-cardwell• 14 years ago

Call centre: Can you please provide the answer to the secret question.

Social engineer: sigh, I know this is going to sound really strange, but I just pick random words when I set up secret questions, and I'm not sure what I used with you. If it helps, it will just be a set of random words that make no sense...

Call centre: Ok, I've spoken to my supervisor and he said that, seeing as you kind of know what it's like, and seeing as you have the name and address, I can reset your password. What number would you like me to SMS it to?

Argorak• 14 years ago

Thats brilliant. A big opportunity to introduce call centre agents to Monty Python quotes!

tokenadult• 14 years ago

Original date of this article: April 30, 2010. Too bad it wasn't April 1st.

Q: What is your mother's maiden name?

A: I never use my mother's REAL maiden name in a security question; that is much too easy to look up with Google.

jtheory2• 14 years ago

Entertaining (though I've already read this one...).

I have a more interesting game I play with bank security questions that's more useful, though -- and applies to the most common usage (where the bank provides the question to you).

Simply this -- for each question, imagine how easily you could guess the answer even knowing nothing about the account owner. I'm not talking about real analysis here, just roughly mapping out the answer space.

For example, "In what city/town did ___?" is a common question. Well, if it's a US bank, probably you're dealing with US cities, and there are fewer than 20K. (Already, whoa: a three character alphanumeric password has 10 times the possibilities). Then of course cities should be weighted by population, so since NYC is biggest... well, New York has 8.3 million of the USA's 311.6 million population, the answer to this question will be New York City about 2.6% of the time.

"What's the first name of your [specified grandparent]?" is another good one. How diverse are first names, generally, particularly a few generations back? Of course there's a long tail, but otherwise... not that diverse, and it's trivial to find stats on most common names in the early 1900s. I've never chosen this question even before I started thinking hard about security, because it was blazingly obviously a bad question -- the banks would ask for my maternal grandfather's name, and I was named after him.

Fun, no?

suresk• 14 years ago

Here is a worse one:

> What is the make of your first car?

The number of relatively common car makers is really low, and when you factor in the fact that most people don't get a really high-end car as their first car, 5 or 6 makers are going to cover a really high percentage (Ford, Chevrolet, Toyota, and Honda would cover most, I'd guess). If you factor in make AND model, we're still talking in the low hundreds of possibilities.

Good security questions are really, really hard to come up with and should, IMHO, really only be used as an addition to a password - not as a way around one.

troymc• 14 years ago

For the same reason, this one is awful:

What is your favourite colour?

(There are lots of colour names, but most people will stick to the most common ten or so.)

antidoh• 14 years ago

> What is the make of your first car?

Winston Churchill.

jasomill• 14 years ago

Q: Ennyn Durin aran Moria. Pedo mellon a minno.

A: Mellon!

chris_wot• 14 years ago

While entertaining, choosing the question "What is the air speed velocity of a laden swallow?" is not particularly good security.

harshreality• 14 years ago

That applies to many of them. It's clearly just for fun. Quotes are no good. If it's a quote from media like music, movies, book, or TV, the response can usually be googled, if it's not known already. If it's a personal quote, someone who knows you might know it.

bajsejohannes• 14 years ago

I almost always pick something like "What's your favorite color?" and answer with random noise (say "a3tcuh487wchaowiudh23doch3298ahraui"). The rationale is that if I forget my password, I'll likely forget the secret question as well. I only want the secret question to be as hard, or harder, to guess than my password.

I wonder though, if the human at the other end will accept "just a bunch of letters and numbers" as a correct answer.

polynomial2• 14 years ago

While I have a hard time imagining Bruce just lifted someone else's blog post without crediting (more likely it was passed on to him in conversation?), this post predates Schneier's by over a year: http://tcoverride.blogspot.com/2011/05/security-questions.ht....

maxerickson• 14 years ago

Check the Schneier date again.

polynomial2• 14 years ago

lol, repost. My bad.

desigooner• 14 years ago

Hardly. Rather, it would seem to be the other way around.

T-hawk• 14 years ago

My bank has a particularly horrible one:

"What sports team do you most like to see lose?"

Especially considering it's a regional bank in the northeast US, you can probably hit well over 90% of accounts using less than a dozen answers.

wherewhenwhy• 14 years ago

Why the hell is anyone answering "What was your mother's grandfather's maiden/first name" or "What city were you born in" with real answers, or even real names/cities??

Schneier on Security: Fun with Secret Questions

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