Mental Models & Security: Thinking Like a Hacker

In the world of information security, people are often told to "think like a hacker." The problem is, if you think of a hacker within a very narrow definition (e.g., someone who only breaks Web applications), it leads to a counterproductive way of thinking and conducting business.

A little knowledge is a dangerous thing, not least because isolated facts don't stand on their own very well. As legendary investor Charlie Munger once said:

Well, the first rule is that you can't really know anything if you just remember isolated facts and try and bang 'em back. If the facts don't hang together on a latticework of theory, you don't have them in a usable form.

You've got to have models in your head. And you've got to array your experience both vicarious and direct on this latticework of models. ...

[You've] got to have multiple models because if you just have one or two that you're using, the nature of human psychology is such that you'll torture reality so that it fits your models, or at least you'll think it does. …

This is worth bearing in mind for security pros.

When we look at the thought process of a (competent) security professional, it encompasses many mental models. These don't relate exclusively to hacking or wider technology, but instead cover principles that have broader applications.

Let's look at some general mental models and their security applications.

1. Inversion
Difficult problems are best solved when they are worked backward. Researchers are great at inverting systems and technologies to illustrate what the system architect should have avoided. In other words, it's not enough to think about all the things that can be done to secure a system; you should think about all the things that would leave a system insecure.

From a defensive point of view, it means not just thinking about how to achieve success, but also how failure would be managed.

2. Confirmation Bias
What people wish, they also believe. We see confirmation bias deeply rooted in applications, systems, and even entire businesses. It's why two auditors can assess the same system and arrive at vastly different conclusions regarding its adequacy.

Confirmation bias is extremely dangerous from a defenders' perspective, and it clouds judgment. This is something hackers take advantage of all the time. People often fall for phishing emails because they believe they are too clever to fall for one. Reality sets in after it's too late.

3. Circle of Competence
Most people have a thing that they're really good at. But if you test them in something outside of this area, you may find that they're not well-rounded. Worse, they may even be ignorant of their own ignorance.

When we examine security as a discipline, we realize it's not a monolithic thing. It consists of countless areas of competence. A social engineer, for example, has a specific skill set that differs from a researcher with expertise in remotely gaining access to SCADA systems.

The number of tools in a tool belt isn't important. What's far more important is knowing the boundaries of one's circle of competence.

Managers building security teams should evaluate the individuals in the team and build the department's circle of competence. This can also help identify where gaps are that must be filled.

4. Occam's Razor
Occam's razor can be summarized like this: "Among competing hypotheses, the one with the fewest assumptions should be selected."

It's a principle of simplicity that's relevant to security on many levels. Often hackers will use simple, tried-and-tested methods to compromise a company's systems: the infected USB drive in the parking lot or the perfectly crafted spearphishing email that purports to be from the finance department.

While there are also complex and advanced attack avenues, these are not likely to be used against most companies. By using Occam's razor, attackers can often compromise targets faster and cheaper. The same principles can and should be applied when securing organizations.

5. Second-Order Thinking
Second-order thinking means to consider that effects have effects. This forces you to think long-term when considering what action to take. The question to ask is, "If I do X, what will happen after that?"

It's easy in the security world to give first-order advice. For example, keeping up to date with security patches is good advice. But without second-order thinking, this can lead to poor decisions with unforeseen consequences. It's vital that security professionals consider all implications before executing. For example, "What impact will there be on downstream systems if we upgrade the OS on machine X?"

6. Thought Experiments
A technique popularized by Albert Einstein, the thought experiment is a way to logically carry out a test in one's own head that would be difficult or impossible to perform in real life. In security, this is usually used during "tabletop" exercises or when risk modeling. It can be extremely effective when used in conjunction with other mental models.

The purpose isn't necessarily to reach a definitive conclusion but to encourage challenging thoughts and to push people outside of their comfort zones.

7. Probabilistic Thinking (Bayesian Updating)
The world is dominated by probabilistic outcomes, as distinguished from deterministic ones. Although we cannot predict the future with great certainty, we often subconsciously make decisions based on probabilities. For example, when crossing the road, we believe there's a low risk of being hit by a car. The risk exists, but if you've looked for traffic, you are confident that you can cross.

The Bayesian method says that one should consider all prior relevant probabilities and then incrementally update them as newer information arrives. This method is especially productive given the fundamentally nondeterministic world we experience: we must use both prior odds and new information to arrive at our best decisions.

While there may not be a simple answer to what it means to "think like a hacker," the use of mental models to build frameworks of thought can help avoid the pitfalls associated with approaching every problem from the same angle.

I've listed seven mental models here, some which you may already be familiar with and others you could try. Please share any of your favorite security and hacker mental models and problem-solving techniques in the comments.  

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