Bringing clarity to chaos: Sounil Yu on the Cyber Defence Matrix

“Its strength is its simplicity. It provides scaffolding on which deeper insights could be layered.”

Cybersecurity has always been a complex field. It’s full of overlapping tools, competing (and not always transparent) vendor claims, and shifting threats that make clarity feel almost impossible. 

But what if there were a way to cut through the noise; a simple, visual framework that could map your defences and help you make smarter security decisions?

That’s exactly what Black Hat MEA 2025 speaker Sounil Yu (Chief AI Officer at Knostic) set out to create with the Cyber Defense Matrix. Described by Yu as a ‘periodic table for cybersecurity,’ this framework has become a powerful tool for CISOs, educators, vendors, investors, and practitioners across the industry. 

We asked Yu to share the origin story of the Matrix, and reflect on the unexpected use cases that have emerged since its launch. 

Can you describe the Cyber Defense Matrix in a paragraph or two?

“It’s a simple mental model that helps organisations understand, organise, and evaluate their cybersecurity capabilities. It aligns the five operational functions of the NIST Cybersecurity Framework (Identify, Protect, Detect, Respond, and Recover) against five asset classes (Devices, Applications, Networks, Data, and Users.) 

“By laying out security capabilities, skillsets, and processes in this simple grid, the Cyber Defense Matrix provides clarity on where one’s defenses are strong, where overlaps exist, and where gaps may remain. It is a simple but powerful way to visualise the complex cybersecurity landscape.

“Beyond categorisation, it also serves as a decision-making and communications tool. It helps CISOs and practitioners make risk management decisions about what should be covered, rationalise investments, avoid blind spots…in many ways, I think it’s a meaningful ‘periodic table’ for cybersecurity, turning something that is typically disorganised and chaotic into a nice visual structure.”

What was the core problem that led you to develop this framework?

“When I was the Chief Security Scientist at Bank of America, I had many vendors approach me to consider buying their product. Unfortunately, the vendors often used overlapping or inconsistent language to describe their capabilities. Cybersecurity is already complex and the imprecise language only made it more difficult to compare solutions or see how they fit into our organisation’s cyber defense strategy. I needed a common reference point to map and evaluate the countless vendors in our industry.

“The Cyber Defense Matrix emerged as a way to simplify the landscape and offer a mental model with a unifying structure that could cut through the noise and provide clarity on what specific problem each vendor was trying to address.”

What were your goals initially in terms of use cases/users - and how does that compare to the real world use cases/users that adopted the Matrix after you created it?

“Initially, I designed it to help me organise tools, understand coverage, and communicate effectively with other stakeholders and teams about our gaps and opportunities. Along the way, I discovered several other use cases, which I’ve shared at various conferences, workshops, and in a book that I published in 2021.

“Originally, I had thought that only larger enterprises would adopt the Cyber Defense Matrix. But it turned out to be useful for a much wider audience. Educators adopted it as a teaching aid; vendors used it to position their products; analysts and investors applied it to evaluate markets and new startup opportunities; Managed Service Providers (MSP) leveraged it to upsell security services; and security teams of all sizes leveraged it for gap analysis and strategic planning. Its versatility and simplicity allowed it to resonate far beyond my initial expectations.”

Can you share one or two challenges you had when it came to communicating the value of the Matrix to potential adopters?

“One of my favourite quotes is from George Box: ‘All models are wrong, but some are useful.’ The Cyber Defense Matrix is not the perfect model for all things in cybersecurity. There are much better models for consideration depending upon the goals that you wish to achieve. But that said, the Cyber Defense Matrix has turned out to be quite useful for many different use cases. Its strength is its simplicity. It provides scaffolding on which deeper insights could be layered.

“Another challenge was encouraging consistency in interpretation and application. People often tried to fit their preferred tools or narratives into the Matrix in ways that didn’t align with its design. I learned that adoption required not just the framework itself but also education, examples, and patience to help people see how to apply it faithfully and effectively. This is why I run workshops at the RSA Conference in San Francisco every year and other random cities as time permits.”

How do you see this framework evolving in the future?

“It will continue to evolve as our technology and threats evolve and as our understanding of cybersecurity itself matures. While the core structure seems to remain stable, I see opportunities to enrich it with new use cases and applications, such as applying it to resilience, mapping human factors, or integrating emerging domains like AI and supply chain security.

“I also advise a few vendors that have incorporated the Cyber Defense Matrix into their product (including ESProfiler and RealCISO), providing an interactive and data-driven implementation. With automation and visualisation tools, organisations can dynamically map their environments onto the Cyber Defense Matrix, enabling real-time insights into coverage, risk, and investment priorities. In this way, it can continue to serve as both a teaching tool and an operational compass.”

And finally, if you could go back to the beginning of your career and tell yourself one thing you wish you'd known then...what would it be?

“I used to be more rigid in my thinking around how the Cyber Defense Matrix should be interpreted and used. But I realised that I was making it more complex than it needed to be. I would tell my past self that clarity is more valuable than complexity. The most enduring impact comes from making the complex understandable without losing the essence of helping people make better informed decisions based on what the Cyber Defense Matrix shows.

“Making better decisions is what drove me to create the framework itself. But in my search for the ‘best decision’, I ended up forgetting that ‘perfect is the enemy of good.’ If I had remembered and embraced this principle sooner, I would have looked for ways earlier in my journey to build more simple, scalable frameworks that bring order to chaos. It’s a lesson I now try to carry into everything I create.”

Thanks to Sounil Yu at Knostic. Join us at Black Hat MEA 2025 to learn directly from the leading minds in cybersecurity.