July 30, 2019

Research is “Skewing up”

Filed under: Artificial Intelligence,Security Article Reviews,Security Intelligence — @ 30th of July 2019, 18:19

Over the weekend I was catching up on some reading and came about the “Deep Learning and Security Workshop (DLS 2019)“. With great interest I browsed through the agenda and read some of the papers / talks, just to find myself quite disappointed.

It seems like not much has changed since I launched this blog. In 2005, I found myself constantly disappointed with security articles and decided to outline my frustrations on this blog. That was the very initial focus of this blog. Over time it morphed more into a platform to talk about security visualization and then artificial intelligence. Today I am coming back to some of the early work of providing, hopefully constructive, feedback to some of the work out there.

The researcher paper I am looking at is about building a deep learning based malware classifier. I won’t comment on the fact that every AV company has been doing this for awhile (but learned from their early mistakes of not engineering ‘intelligent’ features). I also won’t discuss the machine learning architecture that is introduced. What I will argue is the approach that was taken and the conclusions that were drawn:

  • The paper uses a data set that has no ground truth. Which, in network security is very normal. But it needs to be taken into account. Any conclusion that is made is only relative to the traffic that the algorithm was tested, at the time of testing and under the used configuration (IDS signatures). The paper doesn’t discuss adoption or changes over time. It’s a bias that needs to be clearly taken into account.
  • The paper uses a supervised approach leveraging a deep learner. One of the consequences is that this system will have a hard time detecting zero days. It will have to be retrained regularly. Interestingly enough, we are in the same world as the anti virus industry when they do binary classification.
  • Next issue. How do we know what the system actually captures and what it does not?
    • This is where my recent rants on ‘measuring the efficacy‘ of ML algorithms comes into play. How do you measure the false negative rates of your algorithms in a real-world setting? And even worse, how do you guarantee those rates in the future?
    • If we don’t know what the system can detect (true positives), how can we make any comparative statements between algorithms? We can make a statement about this very setup and this very data set that was used, but again, we’d have to quantify the biases better.
  • In contrast to the supervised approach, the domain expert approach has a non-zero chance of finding future zero days due to the characterization of bad ‘behavior’. That isn’t discussed in the paper, but is a crucial fact.
  • The paper claims a 97% detection rate with a false positive rate of less than 1% for the domain expert approach. But that’s with domain expert “Joe”. What about if I wrote the domain knowledge? Wouldn’t that completely skew the system? You have to somehow characterize the domain knowledge. Or quantify its accuracy. How would you do that?

Especially the last two points make the paper almost irrelevant. The fact that this wasn’t validated in a larger, real-world environment is another fallacy I keep seeing in research papers. Who says this environment was representative of every environment? Overall, I think this research is dangerous and is actually portraying wrong information. We cannot make a statement that deep learning is better than domain knowledge. The numbers for detection rates are dangerous and biased, but the bias isn’t discussed in the paper.

:q!

July 24, 2019

Causality Research in AI – How Does My Car Make Decisions?

Filed under: Artificial Intelligence,Security Intelligence — @ 24th of July 2019, 14:19

Before even diving into the topic of Causality Research, I need to clarify my use of the term #AI. I am getting sloppy in my definitions and am using AI like everyone else is using it, as a synonym for analytics. In the following, I’ll even use it as a synonym for supervised machine learning. Excuse my sloppiness …

Causality Research is a topic that has emerged from the shortcomings of supervised machine learning (SML) approaches. You train an algorithm with training data and it learns certain properties of that data to make decisions. For some problems that works really well and we don’t even care about what exactly the algorithm has learned. But in certain cases, we really would like to know what the system just learned. Your self-driving car, for example. Wouldn’t it be nice if we actually knew how the car makes decisions? Not just for our own peace of mind, but also to enable verifyability and testing.

Here are some thoughts about what is happening in the area of causality for AI:

  • This topic is drawing attention because people are having their blinders on when defining what AI is. AI is more than supervised machine learning, and a number of the algorithms in the field, like belief networks, are beautifully explainable.
  • We need to get away from using specific algorithms as the focal point of our approaches. We need to look at the problem itself and determine what the right solution to the problem is. Some of the very old methods like belief networks (I sound like a broken record) are fabulous and have deep explainability. In the grand scheme of things, only few problems require supervised machine learning. 
  • We are finding ourselves in a world where some people believe that data can explain everything. It cannot. History is not a predictor of the future. Even in experimental physics, we are getting to our limits and have to start understanding the fundamentals to get to explainability. We need to build systems that help experts encode their knowledge and augments human cognition by automating tasks that machines are good at.

The recent Cylance faux pas is a great example why supervised machine learning and AI can be really really dangerous. And it brings up a different topic that we need to start exploring more, which is how we measure the efficacy or precision of AI algorithms. How do we assess the things a given AI or machine learning approach misses and what are the things it classifies wrong? How does one compute these metrics for AI algorithms? How do we determine whether one algorithm is better than another. For example, the algorithm that drives your car. How do you know how good it is? Does a software update make it better? How much? That’s a huge problem in AI and ‘causality research’ might be able to help develop methods to quantify efficacy.