Practicing a science of security

Recently, at NSPW 2017, Tyler Moore, David Pym, and I presented our work on practicing a science of security. The main argument is that security work – both in academia but also in industry – already looks a lot like other sciences. It’s also an introduction to modern philosophy of science for security, and a survey of the existing science of security discussion within computer science. The goal is to help us ask more useful questions about what we can do better in security research, rather than get distracted by asking whether security can be scientific.

Most people writing about a science of security conclude that security work is not a science, or at best rather hopefully conclude that it is not a science yet but could be. We identify five common reasons people present as to why security is not a science: (1) experiments are untenable; (2) reproducibility is impossible; (3) there are no laws of nature in security; (4) there is no single ontology of terms to discuss security; and (5) security is merely engineering.

Through our introduction to modern philosophy of science, we demonstrate that all five of these complaints are misguided. They rely on an old conception of what counts as science that was largely abandoned in the 1970s, when the features of biology came to be recognized as important and independent from the features of physics. One way to understand what the five complaints actually allege is that security is not physics. But that’s much less impactful than claiming it is not science.

More importantly, we have a positive message on how to overcome these challenges and practice a science of security. Instead of complaining about untenable experiments, we can discuss structured observations of the empirical world. Experiments are just one type of structured observation. We need to know what counts as a useful structure to help us interpret the results as evidence. We provide recommendations for use of randomized control trials as well as references for useful design of experiments that collect qualitative empirical data. Ethical constraints are also important; the Menlo Report provides a good discussion on addressing them when designing structured observations and interventions in security.

Complaints about reproducibility are really targeted at the challenge of interpreting results. Astrophysics and paleontology do not reproduce experiments either, but are clearly still sciences. There are different senses of “reproduce,” from repeat exactly to corroborate by similar observations in a different context. There are also notions of statistical reproducibility, such as using the right tests and having enough observations to justify a statistical claim. The complaint is unfair in essentially demanding all the eight types of reproducibility at once, when realistically any individual study will only be able to probe a couple types at best. Seen with this additional nuance, security has similar challenges in reproducibility and interpreting evidence as other sciences.

A law of nature is a very strange thing to ask for when we have constructed the devices we are studying. The word “law” has had a lot of sticking power within science. The word was perhaps used in the 1600s and 1700s to imply a divine designer, thereby making the Church more comfortable with the work of the early scientists. The intellectual function we really care about is that a so-called “law” lets us generalize from particular observations. Mechanistic explanations of phenomena provide a more useful and approachable goal for our generalizations. A mechanism “for a phenomenon consists of entities (or parts) whose activities and interactions are organized so as to be responsible for the phenomenon” (pg 2).

MITRE wrote the original statement that a single ontology was needed for a science of security. They also happen to have a big research group funded to create such an ontology. We synthesize a more realistic view from Galison, Mitchell, and Craver. Basically, diverse fields contribute to a science of security by collaboratively adding constraints on the available explanations for a phenomenon. We should expect our explanations of complex topics to reflect that complexity, and so complexity may be a mark of maturity, rather than (as is commonly taken) a mark that security has as yet failed to become a science by simplifying everything into one language.

Finally, we address the relationship between science and engineering. In short, people have tried to reduce science to engineering and engineering to science. Neither are convincing. The line between the two is blurry, but it is useful. Engineers generate knowledge, and scientists generate knowledge. Scientists tend to want to explain why, whereas engineers tend to want to predict a change in the future based on something they make.  Knowing why may help us make changes. Making changes may help us understand why. We draw on the work of Dear and Leonelli to bring out this nuanced, mutually supportive relationship between science and engineering.

Security already can accommodate all of these perspectives. There is nothing here that makes it seem any less scientific than life sciences. What we hope to gain from this reorientation is to refocus the question about cybersecurity research from ‘is this process scientific’ to ‘why is this scientific process producing unsatisfactory results’.