Secure Design Principles

Basic and simple Objectives that should be kept in mind during the development of secure systems. Following these Principles should help to mitgate common security issues.

A system is only as secure as its weakest component. Attackers target vulnerabilities like weak passwords or outdated software. Strengthen these weak spots first.Example: Fixing an unpatched server before upgrading a firewall.

Use multiple layers of security (e.g., firewalls, encryption, access controls). If one layer fails, others still protect the system. Example: A bank using alarms, guards, and vaults to secure money.

When systems fail, they should do so without exposing vulnerabilities. Avoid leaving doors open for attackers during crashes or errors. Example: A login system that locks accounts after repeated failures instead of revealing user details.

Give users/programs only the minimum access needed to perform tasks, and only for as long as necessary. Example: A customer support agent can view orders but cannot delete them.

Divide the system into isolated parts to limit damage if one part is broken through. Example: Separating user accounts and admin controls in a web app to prevent total system takeover.

Complex designs increase bugs and security flaws. Simplicity makes systems easier to secure and maintain. Example: Using straightforward code instead of overly clever solutions.

Minimize data collection and protect user information. Balance usability with privacy. Example: An app asking for location access only when necessary, not always tracking users.

Secrets (e.g., passwords, API keys) in code are easy to extract. Avoid relying on "hidden" data for security. Example: Storing encryption keys in secure vaults instead of hardcoding them.

Assume all external inputs and systems are untrustworthy. Verify and restrict access. Example: Validating user inputs to prevent SQL injection attacks.

Trust widely reviewed and tested solutions (e.g., open-source libraries) over untested, custom ones. Example: Using AES encryption (peer-reviewed) instead of inventing a new algorithm.

• secure the weakest link

• Practise defense in depth

• Fail securely

• Keep it simple