Tag: hacking

This blog post is about password security. If you don’t run a website and you just want to know what you should do to protect yourself, jump to the end.

I’d like to tell you a story about a place called Internetland. Internetland is a little bit like the town or country that you live in, but there’s one really important difference: in Internetland, everybody is afflicted with an unusual disorder called prosopagnosia, or “face-blindness”. This means that, no matter how hard they try, the inhabitants of Internetland can’t recognise each other by looking at one another: it’s almost as if everybody was wearing masks, all the time.

Denied the ability to recognise one another on sight, the people of Internetland have to say out loud who they are when they want to be identified. As I’m sure you can imagine, it’d be very easy for people to pretend to be one another, if they wanted. There are a few different ways that the inhabitants get around that problem, but the most-common way is that people agree on and remember passwords to show that they really are who they claim to be.

Alice’s Antiques

Alice runs an antiques store in Internetland. She likes to be able to give each customer a personalised service, so she invites her visitors to identify themselves, if they like, when they come up to the checkout. Having them on file means that she can contact them about special offers that might interest them, and she can keep a record of their address so that the customer doesn’t have to tell her every time that they want a piece of furniture delivered to their house.

One day, Bob came by. He found a nice desk and went to the checkout to pay for it.

“Hi,” said Alice, “Have you shopped here before?” Remember that even if he’d visited just yesterday, she wouldn’t remember him, so crippling is her face-blindness.

“No,” replied Bob, “First time.”

“Okay then,” Alice went on, “Would you like to check out ‘as a guest’, or would you like to set up an account so that I’ll remember you next time?”

Bob opted to set up an account: it’d only take a few minutes, Alice promised, and would allow him to check out faster in future. Alice gave Bob a form to fill in:

Alice took the form and put it into her filing cabinet.

The following week, Bob came by Alice’s Antiques again. When he got to the checkout, Alice again asked him if he’d shopped there before.

“Yes, I’ve been here before,” said Bob, “It’s me: Bob!”

Alice turned to her filing cabinet and pulled out Bob’s file. This might sound like a lot of work, but the people of Internetland are very fast at sorting through filing cabinets, and can usually find what they’re looking for in less than a second. Alice found Bob’s file and, looking at it, challenged Bob to prove his identity:

“If you’re really Bob – tell me your password!”

“It’s swordfish1,” came the reply.

Alice checked the form and, sure, that was the password that Bob chose when he registered, so now she knew that it really was him. When he asked for a set of chairs he’d found to be delivered, Alice was able to simply ask, “You want that delivered to 1 Fisherman’s Wharf, right?”, and Bob just nodded. Simple!

Evil Eve

That night, a burglar called Eve broke into Alice’s shop by picking the lock on the door (Alice never left money in the till, so she didn’t think it was worthwhile buying a very good lock). Creeping through the shadows, Eve opened up the filing cabinet and copied out all of the information on all of the files. Then, she slipped back out, locking the door behind her.

Alice’s shop has CCTV – virtually all shops in Internetland do – but because it wasn’t obvious that there had been a break-in, Alice didn’t bother to check the recording.

Now Eve has lots of names and passwords, so it’s easy for her to pretend to be other Internetlanders. You see: most people living in Internetland use the same password at most or all of the places they visit. So Eve can go to any of the other shops that Bob buys from, or the clubs he’s part of, or even to his bank… and they’ll believe that she’s really him.

One of Eve’s favourite tricks is to impersonate her victim and send letters to their friends. Eve might pretend to be Bob, for example, and send a letter to his friend Charlie. The letter might say that Bob’s short on cash, and ask if Charlie can lend him some: and if Charlie follows the instructions (after all, Charlie trusts Bob!), he’ll end up having his money stolen by Eve! That dirty little rotter.

So it’s not just Bob who suffers for Alice’s break-in, but Charlie, too.

Bob Thinks He’s Clever

Bob thinks he’s cleverer than most people, though. Rather than use the same password everywhere he goes, he has three different passwords. The first one is his “really secure” one: it’s a good password, and he’s proud of it. He only uses it when he talks to his bank, the tax man, and his credit card company – the stuff he thinks is really important. Then he’s got a second password that he uses when he goes shopping, and for the clubs he joins. A third password, which he’s been using for years, he reserves for places that demand that he chooses a password, but where he doesn’t expect to go back to: sometimes he joins in with Internetland debates and uses this password to identify himself.

Bob’s approach was cleverer than most of the inhabitants of Internetland, but it wasn’t as clever as he thought. Eve had gotten his medium-security password, and this was enough to persuade the Post Office to let her read Bob’s mail. Once she was able to do this, she went on to tell Bob’s credit card company that Bob had forgotten his password, so they sent him a new one… which she was able to read. She was then able to use this new password to tell the credit card company that Bob had moved house, and that he’d lost his card. The credit card company promptly sent out a new card… to Eve’s address. Now Eve was able to steal all of Bob’s money. “Muhahaha!” chortled Eve, evilly.

But even if Bob hadn’t made the mistake of using his “medium-security” password at the Post Office, Eve could have tried a different approach: Eve would have pretended to be Alice, and asked Bob for his password. Bob would of course have responded, saying “It’s ‘swordfish1’.”

Then Eve would have done something sneaky: she’d have lied and said that was wrong. Bob would be confused, but he’d probably just think to himself, “Oh, I must have given Alice a different password.”

“It must be ‘haddock’, then,” Bob would say.

“Nope; wrong again,” Eve would say, all the while pretending to be Alice.

“Surely it’s not ‘h@mm3rHead!’, is it?” Bob would try, one last time. And now Eve would have all of Bob’s passwords, and Bob would just be left confused.

Good Versus Eve

What went wrong in Internetland this week? Well, a few things did:

Alice didn’t look after her filing cabinet

For starters, Alice should have realised that the value of the information in her filing cabinet was worth at least as much as money would be, to the right kind of burglar. It was easy for her to be complacent, because it wasn’t her identity that was most at risk, but that of her customers. Alice should have planned her security in line with that realisation: there’s no 100% certain way of stopping Eve from breaking in, but Alice should have done more to make it harder for Eve (a proper lock, and perhaps a separate, second lock on the filing cabinet), and should have made it so that Eve’s break-in was likely to be noticed (perhaps skimming through the security tapes every morning, or installing motion sensors).

But the bigger mistake that Alice made was that she kept Bob’s password in a format that Eve could read. Alice knew perfectly well that Bob would probably be using the same password in other places, and so to protect him she ought to have kept his password encrypted in a way that would make it virtually impossible for Eve to read it. This, in combination with an effort to insist that her customers used good, strong passwords, could have completely foiled Eve’s efforts, even if she had managed to get past the locks and CCTV un-noticed.

Here in the real world: Some of Alice’s mistakes are not too dissimilar to the recently-publicised mistakes made by LinkedIn, eHarmony, and LastFM. While these three giants did encrypt the passwords of their users, they did so inadequately (using mechanisms not designed for passwords, by using outdated and insecure mechanisms, and by failing to protect stolen passwords from bulk-decryption). By the way: if you have an account with any of these providers, you ought to change your password, and also change your password anywhere else that uses the same password… and if this includes your email, change it everywhere else, too.

Bob should have used different passwords everywhere he went

Good passwords should be long (8 characters should be an absolute minimum, now, and Bob really ought to start leaning towards 12), complex (not based on a word in any dictionary, and made of a mixture of numbers, letters, and other characters), and not related to you (dates of birth, names of children, and the like are way out). Bob had probably heard all of that a hundred times.

But good passwords should also be unique. You shouldn’t ever use the same password in two different places. This was Bob’s mistake, and it’s the mistake of almost everybody else in Internetland, too. What Bob probably didn’t know was that there are tools that could have helped him to have a different password for everybody he talked to, yet still been easier than remembering the three passwords he already remembered.

Here in the real world: There are some really useful tools to help you, too. Here are some of them:

• LastPass helps you generate secure passwords, then stores encrypted versions of them on the Internet so that you can get at them from anywhere. After a short learning curve, it’s ludicrously easy to use. It’s free for most users, or there are advanced options for paid subscribers.
• KeePass does a similar thing, but it’s open source. However, it doesn’t store your encrypted passwords online (which you might consider to be an advantage), so you have to carry a pen drive around or use a plugin to add this functionality.
• SuperGenPass provides a super-lightweight approach to web browser password generation/storing. It’s easy to understand and makes it simple to generate different passwords for every site you use, without having to remember all of those different passwords!
• One approach for folks who like to “roll their own” is simply to put a spreadsheet or a text file into a TrueCrypt (or similar) encrypted volume, which you can carry around on your pendrive. Just decrypt and read, wherever you are.
• Another “manual” approach is simply to use a “master password” everywhere, prefixed or suffixed with a (say) 4-5 character modifier, that you vary from site to site. Keep your modifiers on a Post-It note in your wallet, and back it up by taking a picture of it with your mobile phone. So maybe your Skype suffix is “8Am2%”, so when you log into Skype you type in your master password, plus that suffix. Easy enough that you can do it even without a computer, and secure enough for most people.

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