Secure Design and Development

Life Cycle Support

Both secure design and coding should be integral parts of the software development life cycle (SDLC). This means that security considerations are continuously addressed throughout the following stages:

• Requirements Gathering: Security requirements are defined alongside functional requirements.

• Design: Systems are designed with security controls and defenses built into their architecture.

• Development: Developers follow secure coding practices and use automated tools to detect security flaws.

• Testing: Security testing, including vulnerability assessments and penetration testing, is performed to validate that the system is secure.

• Deployment: Secure deployment practices are followed, such as using encryption, configuring firewalls, and securing servers.

• Maintenance and Monitoring: After deployment, regular updates, patching, and monitoring are necessary to ensure ongoing security.

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Secure Design

Secure design refers to the incorporation of security features into the blueprint of software and systems, from the earliest stages of development. This is a proactive approach where security concerns are addressed at the structural level, aiming to mitigate risks before they materialize. Key elements of secure design include:

• Secure Design and Coding: Secure design and coding are fundamental principles of cybersecurity, ensuring that software and systems are built with resilience against security threats. With the incorporation of security best practices and industry recommendations your system is resilient against cyberattacks.

• Risk Assessment: Understanding possible threats and weaknesses during a risk assessment in the early design stages is crucial. By identifying how an attacker could take advantage of these weaknesses, designers can put in place safeguards to reduce risks before the product is launched. As part of risk assessment process, you can use automatic tools that scan source code, or firmware scanners that scan binary, including third party components. Assess your current situation here.

• Minimization of Attack Surface: The attack surface refers to all possible points where an attacker could exploit the system. Secure design principles seek to reduce the number of potential entry points by limiting the amount of exposed code and reducing unnecessary features. By default, the device should expose as few services, ports, and functionalities as possible. Limit the functionality of the device to the minimum required for its operation. For example, remove debug tools and utilities that you need only for troubleshooting in lab. In some cases attackers were able to exploit debug interfaces (examples are UART and JTAG) which left exposed in production, allowing adversaries to bypass security controls.

• Least Privilege: Restricting user and application access to the minimum required for their specific functions. This reduces the potential impact of a breach. Ensure that role-based access management is incorporated into your system, with careful control to prevent unauthorized access to root-level privileges.

• Access Control: A well-designed network access control policy focuses on restricting access to the device, ensuring that only authorized communications are allowed and data transmission remains secure. Separate control plain and data plain, and verify that the control plain is accessible only for privileged users. Implement TLS (Transport Layer Security) to protect against man-in-the-middle (MiTM) attacks, ensuring the confidentiality and integrity of data in transit.

Look for common tools and capabilities from the industry. For example, a very convenient way is to utilize nftables on Linux-based systems, the policy should control traffic at multiple layers (network and transport) to achieve robust protection. Keep in mind that while nftables supports IP addresses and networks, it does not support domain-based filtering. For domain-level control, consider complementary solutions that introduce an additional configuration layer.

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Industry best practices for secure software development

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Key elements include:

• Password Policy: 
  Weak, hardcoded or default passwords are a common point of exploitation in many cyberattacks.

  • Devices should either:​Force users to create a strong, unique password during initial setup.

  • Generate a random, device-specific password printed on a label, as is often the case with modern home routers.

  • Use MFA (Multi Factor Authentication) if possible, with third-party identity provider to make it more robust.​

• Tamper Protection
  Devices should be designed to detect and resist both physical and logical tampering. Key measures include:

  • Secure Boot & Hardware-Based Root of Trust: Ensures only verified software can execute during startup.

  • Anti-Tamper Mechanisms: Prevents unauthorized physical access to critical components.

  • Example: Implementing Hardware Security Modules (HSM) to protect cryptographic keys from hardware tampering.

  • Relevance: Critical for Operational Technology (OT) systems, including critical infrastructure and healthcare devices.

• Defense in Depth
  A multi-layered security approach ensures that if one control fails, other mechanisms mitigate the risk.

  • Preventive Security Controls: Proactively block threats before they occur.

  • Detective & Monitoring Solutions: Enable rapid response to security breaches, maintaining a robust security posture.

• Fail-Safe Defaults
  Systems should default to a secure state upon failure.

  • IT Environments: Fail-closed (deny access unless explicitly granted).

  • OT/IoT Environments: Fail-open (ensure system continuity but minimize security risks).

  • Example: If an authentication process encounters an error, access should be denied until proper authentication is restored.

• Separation of Duties
  To mitigate internal risks, no single role should have excessive privileges.

  • Reduces the likelihood of insider threats or exploitation.

  • Prevents over-concentration of power in any single user or system component.

• Secure Data Flow
  Sensitive data must be encrypted to prevent unauthorized access.

  • Data at Rest & In Transit: Encrypted to safeguard credentials and sensitive information.

• Authentication & Authorization Patterns

  • Role-Based Access Control (RBAC): Restricts system access based on user roles.

  • Session Management: Ensures secure session handling, reducing hijacking risks.

• Data Protection Patterns

  • Encryption: Ensures confidential data always remains protected.

  • Data Sanitization: Prevents SQL injection and cross-site scripting (XSS) by validating user inputs.

• Input Validation Patterns

  • Whitelisting: Restricts input to expected values, preventing exploits like shell injection, buffer overflows and XSS.

  • Canonicalization: Converts input into a standardized format, preventing security ambiguities. Such as SQL Injection, Directory Traversal attacks, Unicode normalization attacks and case-sensitive authentication bypass.

• Secure Communication Patterns

  • SSL/TLS Protocols: Ensures secure data transmission.

  • Secure Channels: Prevents eavesdropping and man-in-the-middle (MITM) attacks.

• Error Handling & Logging Patterns

  • Fail Securely: Ensures that failures do not create security vulnerabilities.

  • Logging & Auditing: Records security events for threat detection and forensic analysis, ensuring logs do not expose sensitive data.

• Separation of Concerns

  • Layered Architecture: Divides software into independent layers (e.g., presentation, business logic and data access) to limit the impact of breaches.

  • Duty Segregation: Ensures no single entity has complete control over critical operations.

• Secure Object Access

  • Proxy Pattern: Mediates access to sensitive resources, preventing direct unauthorized access.

  • Factory Pattern: Controls object creation to enforce security policies.

• Secure Logging & Monitoring

  • Audit Trails: Maintains logs of significant events (e.g., changes in user roles, access rights) for compliance and forensic analysis.

• Secure State Transitions

  • State Machine Pattern: Ensures controlled, secure system state transitions, preventing attackers from forcing insecure conditions.

• Security in Deployment & Operations

  • Secure Defaults: Configures products with the most secure settings from the outset.

  • Secure Patching: Implements mechanisms for regular, safe updates and patches without exposing systems to additional risks.

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Secure by Default

Products should be designed with security as the default state, reducing the risk of misconfigurations and user errors that could lead to vulnerabilities.

​Key principles include:

• Pre-configured Security Settings: Enable robust security measures by default, minimizing the need for user intervention.

• Automatic Protection: Implement security features that are active from the start, ensuring immediate protection without requiring manual setup.

• Standards-Driven Security: Design products with built-in, up-to-date security measures that align with industry best practices and regulatory requirements.

Secure design refers to the incorporation of security features into the blueprint of software and systems, from the earliest stages of development. This is a proactive approach where security concerns are addressed at the structural level, aiming to mitigate risks before they materialize.