Software security is not something you can bolt on after development. By the time vulnerabilities surface, fixing them often costs exponentially more than addressing them at the design stage. That’s why security must start with architecture and design.
The foundation comes from the Software Security Design Principles first articulated by Saltzer and Schroeder in the 1970s. Despite their age, these principles remain highly relevant today — and when applied in modern contexts like cloud, SaaS, DevSecOps, and AI-driven systems, they help organizations safeguard data, ensure compliance, and build lasting trust with users.
In this article, we’ll explore the 10 fundamental security design principles, update them with modern applications and real-world examples, and give you practical steps to evaluate your systems against them.
Key Aspects of Security Design Software
- Integrity
- Confidentiality
- Availability
Integrity means ensuring that only authorized users can change information, and only in approved ways. For example, suppose a company allows each salesperson to update only their leads while sales managers can update all leads. In that case, an integrity violation happens if a salesperson tries to change someone else’s leads. This breaks the rule that only the original salesperson can update their leads.
Confidentiality involves preventing unauthorized access to certain information or tools. Ideally, those without access shouldn’t even know sensitive information or tools exist. For instance, in the sales lead management system, leads can only be changed by the salesperson who created them.
Availability means that authorized users can access the system when needed. For example, if the lead management system is on a web server, IP restrictions might be used to control access based on IP addresses. If all sales members use the IP address 192.168.1.23 to access the system, then blocking all other IPs would ensure that only authorized users can access the system from an authorized location.
Why Does Security Software Design Matter?
Software security is a critical part of the development process that helps protect applications from potential threats or attacks. Building applications without considering security can lead to disastrous consequences such as data breaches, loss of trust, and financial implications. According to a report by IBM, the global average cost of a data breach in 2023 reached an all-time high of $4.45 million, a 2.3% increase from 2022 and a 15.3% increase from 2020, demonstrating the immense financial risk associated with inadequate security design software.
The Top 10 Software Security Design Principles
These principles form the backbone of secure software development, ensuring the integrity, confidentiality, and availability of applications and data.
1. Least Privilege: Access Only What’s Needed
The principle of least privilege ensures that users, services, and processes have only the permissions necessary to complete their tasks — nothing more. This dramatically reduces the potential damage from insider mistakes, compromised accounts, or malicious actions.
Modern example: In a project management tool like Jira, granting “viewer” or “commenter” roles to most users instead of full administrative access prevents unauthorized changes.
Checklist:
Review all accounts with admin access — do they really need it?
Rotate access keys and credentials regularly.
👉 Key takeaway: The fewer privileges available, the smaller the blast radius of any breach.
2. Fail-Safe Defaults: Secure Out of the Box
Security settings should default to the safest option. Access should be explicitly granted rather than implicitly allowed. If a failure occurs, the system must deny access instead of granting it.
Modern example: A cloud storage service should keep newly uploaded files private until explicitly shared. If a configuration error occurs, the system should not default to public access.
👉 Key takeaway: Make security the default, not an afterthought.
3. Economy of Mechanism: Keep It Simple
Complex systems are harder to secure. The more intricate the design, the more room there is for mistakes and oversights. Simplicity makes systems easier to test, audit, and defend.
Modern example: Instead of building a custom authentication method, organizations should use proven standards like OAuth 2.0 or OpenID Connect. These have been widely vetted and tested against real-world threats.
👉 Key takeaway: Simplicity reduces attack vectors and increases reliability.
4. Complete Mediation: Verify Every Request
Every access request must be checked — not just once, not just at login, but every single time. Caching or assuming earlier checks still apply opens doors for exploitation.
Modern example: A download link should always verify that the user has permission to access the file. If permissions change mid-session, cached access tokens should no longer work.
👉 Key takeaway: Don’t assume past permissions still apply. Always recheck.
5. Open Design: Transparency Builds Trust
Security should never depend on obscurity. A strong system remains secure even when its mechanisms are public. Instead, it relies on robust cryptographic standards and proven design.
Modern example: HTTPS uses TLS, an open standard. Attackers know how it works, yet it remains secure because of strong encryption, not secrecy.
👉 Key takeaway: Use open, well-tested frameworks. “Security by obscurity” is fragile.
6. Separation of Duties: No Single Point of Failure
Critical tasks should require multiple people or systems to complete. This prevents fraud, reduces mistakes, and makes insider attacks more difficult.
Modern example: In financial applications, one employee may initiate a payment, but another must approve it before funds are released. Similarly, in DevOps, code must be peer-reviewed before merging.
👉 Key takeaway: Divide power to multiply security.
7. Least Common Mechanism: Avoid Shared Resources
The more users share a resource, the more opportunities exist for accidental or malicious misuse. Keeping resources separate enhances accountability and reduces risks.
Modern example: Instead of using a single shared “admin” account, assign unique accounts to each administrator. This ensures clear audit trails and prevents shared credential leaks.
👉 Key takeaway: Minimize shared dependencies and maximize accountability.
8. Psychological Acceptability: Security Without Friction
Security mechanisms should align with how users naturally work. If they feel like obstacles, users will find ways around them. Security must be both effective and user-friendly.
Modern example: Multi-factor authentication (MFA) can be cumbersome if poorly implemented. Single Sign-On (SSO) balances security and convenience, making it easier for users to comply.
👉 Key takeaway: Security should enhance, not hinder, the user experience.
9. Defense in Depth: Layered Protection
No single security control is enough. Layered defenses ensure that if one control fails, others remain in place to stop the attack.
Modern example: Even if a phishing attack bypasses MFA, anomaly detection can flag unusual login behavior, and endpoint protection can block malicious payloads.
👉 Key takeaway: Build multiple layers of defense to slow down attackers.
10. Minimize Attack Surface: Less Is More
Every additional feature, API, or integration is a potential attack vector. Reducing the system’s exposure limits opportunities for attackers.
Modern example: Disable unused ports, remove outdated plugins, and restrict APIs to only what is absolutely necessary. Regular penetration testing can help identify overlooked exposures.
👉 Key takeaway: The smaller the attack surface, the safer the system.
Modern Context: Applying Principles in Today’s Software World
While these principles were first written decades ago, they remain essential today. What has changed is the environment in which we apply them:
Cloud & SaaS: Shared responsibility models demand clear access controls, encryption, and monitoring.
DevSecOps: Security must be integrated into CI/CD pipelines, ensuring vulnerabilities are caught early.
Compliance: Standards like SOC 2, ISO 27001, and GDPR require adherence to these principles for certification.
AI & Automation: New tools bring new risks — AI models must be designed with transparency and least privilege in mind.
👉 Key takeaway: Old principles, new challenges. Apply them with a modern lens.
Conclusion: Security Is a Design Choice
Strong software security doesn’t happen by chance — it’s built by design. By following these ten principles, development teams can create systems that are resilient, compliant, and trusted by users.
Action step: Evaluate your current systems against these principles. Where do you excel? Where do gaps remain? Addressing these questions now could prevent costly breaches later.
At SaaSJet, an Atlassian Marketplace Platinum Partner, we prioritize security. Our apps are designed with user safety in mind, ensuring data integrity, confidentiality, and availability. By using our apps, you are using tools built with the best practices for security, contributing to a safer digital world.
We believe that secure software is the future, and we invite you to join us in creating that future.
Stay ahead of the curve. Secure your software, secure your future.