Secure Coding: Principles and Practices

1.3. Why Good People Write Bad Code

Now that we've walked on the dark side, looking at all kinds of things that can go wrong with our software, let's turn our attention back to root causes: why do software flaws occur? Why do good people write bad code?

A great many people believe that vulnerabilities are the spawn of stupid (and probably slothful) programmers. Some adherents to this credo have been customers of ours. Although we have listened respectfully to the arguments for many hours, we disagree.

We believe that, by and large, programmers want to write good software. They surely don't set out with the intention of putting security flaws in their code. Furthermore, because it's possible for a program to satisfy a stringent functional specification and nevertheless bring a vulnerability to life, many (if not most) such flaws have been coded up by people who do their best and are satisfied with (even rewarded for) the result.

What's so hard about writing secure code? Why do vulnerabilities exist at all, let alone persist for decades? Why can't the vendors get it right?

We believe there are three sets of factors that work against secure coding:

Technical factors

The underlying complexity of the task itself

Psychological factors

The "mental models," for example, that make it hard for human beings to design and implement secure software

Real-world factors

Economic and other social factors that work against security quality

This is a hard problem. After a close look at ...