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Security Analogies
Scott Granneman, 2007-05-29

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You may not agree with Hobbes (few today would, in fact), but you have to admit that the drawing of the Leviathan, coupled with Hobbes' words, make his idea crystal clear and easy to fathom. But it's not just in the areas of human study that analogies are used. The human mind seems almost hard-wired for analogies, using them to create and augment perception, problem solving, decision making, explanation, communication, and memory.

This last is especially interesting and resonant in the hands of the brilliant Argentine novelist Jorge Luis Borges (who I last wrote about in "A List of Security Essentials: From Mermaids to Suckling Pigs") and his amazing short story "Funes the Memorious" (which you can read online - go do it!).

In the story, a young man suffers an injury that prevents him from forgetting anything. This might sound cool to computer people, but it actually proves to be a kind of curse to Funes. Since he cannot forget anything, he cannot generalize, and generalization is what allows us to function in the world. As my Psych professor, Dr. Green, explained it to our class, if every dog you saw was perceived as an entirely unique creature, how would you be able to generalize to even form the concept of "dog" in the first place? Borges explains this same concept in "Funes the Memorious", writing

He was ... almost incapable of general, platonic ideas. It was not only difficult for him to understand that the generic term dog embraced so many unlike specimens of differing sizes and different forms; he was disturbed by the fact that a dog at three-fourteen (seen in profile) should have the same name as the dog at three-fifteen (seen from the front). His own face in the mirror, his own hands, surprised him on every occasion. ... Without effort, he had learned English, French, Portuguese, Latin. I suspect, nevertheless, that he was not very capable of thought. To think is to forget a difference, to generalize, to abstract.

Objections to analogies

Of course, not all analogies work, and many are annoying. If I ever hear "Life is like a box of chocolates ... blah blah blah" again, I'll hunt down Tom Hanks and throttle him. And I know that many of you are already protesting that no analogy is perfect, which thereby invalidates the entire idea of analogies in the first place. Chandler Howell put this best when he said "Security is like an analogy. It only works up until the point that someone considers an angle or aspect that you haven't previously considered and accounted for."

Howell is correct. But a good analogy can still serve its purpose, and it can still enlighten people who hear it. Of course no analogy is perfect - but most listeners will grasp the essential similarities regardless. It's the experts, who know the subject of the analogy inside and out, who will see, and focus upon, the imperfections. But analogies aren't for experts; they're for normal folks who are trying to learn from the experts.

Experts also commonly bring up another objection to analogies: that users should learn the authentic concepts first, and analogies merely get in the way. The problem with that assertion, however, is that the vast majority of users simply won't learn the authentic concepts. It's just too difficult in many cases to throw users into the pool and expect them to sink or swim. Remember the purpose of an analogy: take something familiar and relate it to something unfamiliar, and thereby give insight into that unfamiliar idea. When it comes to networking, computers, and security, we're talking about things that are all too often abstractions, and abstractions are easier to understand with analogies.

RMS and Linus use analogies

Besides, it's not as if luminaries in the open source movement, for instance, don't themselves use analogies. Richard M. Stallman often uses a highly effective analogy in explaining free software:

There are four essential freedoms that make the definition of free software ... But these freedoms should not be strange to you. At least, not if you cook, because people who cook enjoy the same four freedoms in using recipes ... The freedom to cook the recipe when you want ... The freedom to study the ingredients and how it’s done, and then change it ... And then the freedom to copy it and hand copies to your friends ... And then... if you cook your version of the recipes for a dinner with your friends, and a friend says 'That was great, can I have the recipe?' you can write down your version of the recipe and make a copy for your friend.

RMS' comparison of the four freedoms of software to those inherent in recipes helps take something people understand - recipes - and applies those concepts to free software, making it simple for almost anyone to grasp the foundations of the free software movement.

Linus Torvalds does the same thing, albeit with a bit more humor. One of his most famous pronouncements is that "Software is like sex; it's better when it's free". That's pretty clear! Even better, and more humorous, is the statement Linus made with tongue firmly planted in cheek when he was introduced at the 4th annual Linux Expo: "My name is Linus, and I am your god". You gotta hand it to the Finns: wry and clever makes a nice combination.

Some good analogies

So analogies can be an effective tool, perhaps an incredibly effective tool. What are some good analogies that we could use to explain concepts of information security to our non-expert friends and family? Flash back to the attempt by Steve Gibson to explain Denial of Service. Pretty bad. When I explain DoS to a class, I start by pointing at a student, and then I go into my shpiel:

Imagine that I decide that I want to make Aubrey's life extremely difficult. I ask all twenty of you to each talk to 20 friends, and spread the following plan: at exactly 10:02 p.m. tomorrow night, everyone call Aubrey's phone number over and over, as fast as you can, for an hour. If she picks up, hang up and dial again. If it's busy, hang up and dial again. Don't stop! Keep the calls going for an hour straight! Now, what's going to be the effect from Aubrey's perspective? Her phone is going to be completely useless. She's going to be so busy responding to her phone ringing that she won't be able to do anything else, and she sure won't be able to make any calls. We'll have completely tied up her phone.

Now imagine if I controlled hundreds or even thousands of computers, and I commanded them all to make requests to another computer at the same time. But unlike humans, which are pretty slow, I could tell these computers to make thousands, tens of thousands, or even hundreds of thousands of requests each second. What would the effect be on that computer trying to field all those requests? About the same effect that all our calls made on Aubrey's phone: it renders it effectively useless. That, in essence, is a Distributed Denial of Service attack. Any questions?

When it comes to explaining why it's not a good idea to have everyone in an organization using Windows, I use an analogy to a biological monoculture. That's not my original idea; Gene Spafford forcefully articulated the idea years ago. But it's a concept people can wrap their minds around. Remind them what the potato blight did to cause the Irish potato famine, and then talk about the effect a new virus or worm could have on a company's network of Windows machines. You can see the lights turning on above their heads.

Finally, if you want to explain what the root user does on a Linux box (and by extension, the Administrator on a Windows machine), read David Baker's well-written and very smart "Root 101: If you don't 'get it,' you probably haven't got it". Baker explains the difference between unprivileged users and root by comparing them to people who live in different kinds of homes. Unprivileged users are like apartment dwellers, while root is like a building superintendent. That's the start of it, and it really is worth reading so you can nick his analogy and use it with your Mom or Dad the next time you're trying to explain why they shouldn't run Windows as Administrator.


Inspired by these analogies and others, I want to announce a new website I've started that's aimed at helping security pros and knowledgeable computer users explain complicated (and even not-so-complicated) concepts to the masses: Security Analogies. Located at http://www.securityanalogies.com, it's a wiki, so any of my readers are free to add, edit, or delete content on the site. With the help of a few friends, I've seeded it with some content already, but it needs more. My readers are smart people, and I'm excited to see what you come up with.

Analogies are powerful tools, and if we work together, we can help build a repository of them that we can all use when we want to explain concepts about computers, networking, and security. To really succeed, however, it will take coordinated teamwork from as many people as possible. My idea may succeed and it may fail, but I think it's worth trying. If people benefit, then it's been worth it. We're not ignorant, so let's not be apathetic. Instead, if you think you can help, join the team and help pitch in!

Scott Granneman teaches at Washington University in St. Louis, consults for WebSanity, and writes for SecurityFocus and Linux Magazine. His latest book, Linux Phrasebook, is in stores now.
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