Thecyber security andsystems engineering concept known as "secure by design" (SbD) mandates that security be incorporated into systems from the outset rather than as an afterthought. Instead of being retrofitted later through patching or external controls, it focuses on integrating security requirements into the architecture itself by incorporating protections at the very beginning of the design process for hardware, software, and services.
Assuming that systems will be attacked, Secure by Design entails limiting their architecture to make compromises challenging, contained, and recoverable. It highlights strategies likedefence in depth, minimisingattack surfaces, theleast privilege principle, and integratingdetection and response mechanisms. SbD treats security as a design constraint on par with performance, usability, and cost, in contrast to reactive approaches that mainly rely on vulnerability management after deployment.
Since significant cyber events, such assupply chain breaches andransomware campaigns, have shown the shortcomings of reactive security, Secure by Design has gained popularity in the twenty-first century. SbD practices are now more frequently required by governments, businesses, and standards organisations in a variety of domains, from consumer Internet of Things (IoT) devices to defence systems. There are similarities between the idea and related paradigms likesafety by design,privacy by design, and the larger trend towards resilient systems engineering.
Secure by Design is based on a number of fundamental concepts:
Security as a design constraint: security specifications must be incorporated into the conceptual design process and upheld at all stages of the project's development.
Anticipate attacks because it is assumed that systems function in hostile environments with active adversaries.
Least privilege: only the most essential permissions are given to users, processes, and services.
Layered security controls and defence in depth lessen the chance of total compromise.
Reduce the attack surface by only exposing necessary features, interfaces, and services.
Constant assurance: security measures need to be continuously tested, observed, and enhanced.
Steer clear of secrecy; strong, open design should be the foundation of security, not proprietary obscurity.
Secure by Design is not a single method; it is a design philosophy that can be used in many different development lifecycles, such as Agile, Waterfall, and DevSecOps. Some well-known frameworks and methods are:
The UK government requires SbD in digital services through the Government Digital Service (GDS) and the Ministry of Defence. This means designing with risk in mind, providing continuous assurance, and reducing attack surfaces.
The Cyber Resilience Act stresses security throughout the life cycles of products in the European Union, which is in line with SbD principles.
Consumer IoT: ETSI TS 103 645 sets security standards that are used in IoT rules in the UK and EU.
While widely endorsed, Secure by Design faces challenges in practice:
Cost and complexity – early investment in security design can increase upfront costs.
Legacy systems – applying SbD to older architectures is often impractical.
Supply chain reliance – third-party software and components may undermine SbD practices.
Human factors – poorly designed controls may cause users to bypass them, reducing effectiveness.
Despite these challenges, SbD is increasingly seen as essential in countering advanced persistent threats (APTs), ransomware, and supply chain attacks.
