12.1 Secure Software Development Lifecycle (SDLC)

The Secure Software Development Lifecycle (SDLC) is a crucial framework for building robust, secure software from the ground up. It integrates security considerations into every phase of development, from planning to maintenance, ensuring a comprehensive approach to safeguarding digital assets.

Risk management plays a key role in the Secure SDLC, involving threat modeling, risk assessment, and security architecture design. These practices help identify potential vulnerabilities, evaluate their impact, and implement appropriate safeguards throughout the software development process.

Secure SDLC Phases

Integrating Security into SDLC Phases

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• SDLC phases incorporate security considerations throughout development process
• Planning phase identifies initial security requirements and risk assessment
• Analysis phase refines security requirements and conducts threat modeling
• Design phase implements secure design principles and creates security architecture
• Implementation phase focuses on secure coding practices and code reviews
• Testing phase includes security testing and vulnerability assessments
• Deployment phase ensures secure configuration and patch management
• Maintenance phase involves continuous monitoring and incident response planning

Establishing Security Requirements

• Security requirements define necessary protective measures for software systems
• Functional security requirements specify security features (authentication, access control)
• Non-functional security requirements address overall system security properties (confidentiality, integrity)
• Compliance requirements ensure adherence to industry standards and regulations (GDPR, PCI DSS)
• Security requirements derived from threat modeling and risk assessment results
• Requirements prioritized based on criticality and potential impact on system security

Applying Secure Design Principles

• Principle of least privilege limits user access to minimum necessary permissions
• Defense in depth implements multiple layers of security controls
• Separation of duties divides critical functions among different users or systems
• Fail-safe defaults ensure system remains in a secure state during failures
• Complete mediation verifies access rights for every access to system resources
• Economy of mechanism keeps security designs as simple and small as possible
• Open design principle relies on security through transparency rather than obscurity
• Psychological acceptability ensures security mechanisms are user-friendly

Implementing Secure Deployment Practices

• Secure configuration management ensures proper system settings and hardening
• Patch management process keeps software and systems up-to-date with security fixes
• Secure communication protocols protect data in transit (TLS, SSH)
• Access control mechanisms restrict system access to authorized users and processes
• Logging and monitoring tools track system activities and detect security incidents
• Backup and recovery procedures safeguard data and ensure business continuity
• Change management processes control modifications to production environments

Risk Management

Conducting Threat Modeling

• Threat modeling identifies potential security threats to a system
• STRIDE model categorizes threats (Spoofing, Tampering, Repudiation, Information disclosure, Denial of service, Elevation of privilege)
• Attack trees visualize potential attack vectors and their relationships
• Data flow diagrams map system components and data movements
• Threat modeling process includes system decomposition, threat identification, and mitigation strategies
• Regular threat modeling updates accommodate system changes and emerging threats

Performing Risk Assessment and Analysis

• Risk assessment evaluates potential impact and likelihood of security threats
• Qualitative risk analysis uses descriptive scales (low, medium, high)
• Quantitative risk analysis assigns numerical values to risks (Annual Loss Expectancy)
• Risk mitigation strategies include risk acceptance, avoidance, transfer, and reduction
• Cost-benefit analysis determines appropriate security investments
• Risk assessment frameworks provide structured approaches (NIST SP 800-30, ISO 27005)
• Continuous risk assessment adapts to changing threat landscapes and vulnerabilities

Developing Security Architecture

• Security architecture defines overall security structure and controls
• Network segmentation isolates critical assets and limits attack surface
• Access control models implement authorization mechanisms (Role-Based Access Control, Attribute-Based Access Control)
• Encryption strategies protect data at rest and in transit
• Security zones establish trust boundaries within the system architecture
• Identity and access management systems manage user authentication and authorization
• Security information and event management (SIEM) centralizes log collection and analysis

Establishing Incident Response Procedures

• Incident response plan outlines steps for handling security incidents
• Incident response team roles and responsibilities clearly defined
• Incident classification system prioritizes response based on severity and impact
• Containment strategies limit damage and prevent incident escalation
• Forensic analysis techniques preserve evidence for investigation
• Communication protocols ensure timely notification of stakeholders
• Post-incident review process identifies lessons learned and improves future responses

Security Validation

Implementing Comprehensive Security Testing

• Vulnerability scanning identifies known weaknesses in systems and applications
• Penetration testing simulates real-world attacks to uncover security flaws
• Fuzz testing inputs random or malformed data to detect application vulnerabilities
• Static application security testing (SAST) analyzes source code for security issues
• Dynamic application security testing (DAST) tests running applications for vulnerabilities
• Security acceptance testing verifies compliance with security requirements
• Continuous security testing integrates automated tests into CI/CD pipelines

Conducting Effective Code Reviews

• Security-focused code reviews identify potential vulnerabilities and coding errors
• Automated code analysis tools scan for common security issues and coding standards violations
• Manual code reviews by security experts provide in-depth analysis of critical components
• Pair programming practices incorporate security considerations during development
• Code review checklists ensure consistent evaluation of security best practices
• Secure coding standards guide developers in writing secure code
• Code review metrics track security issues and improvement over time

Implementing Continuous Monitoring

• Security information and event management (SIEM) systems aggregate and analyze security logs
• Intrusion detection and prevention systems (IDS/IPS) monitor network traffic for malicious activities
• File integrity monitoring detects unauthorized changes to critical system files
• Vulnerability management processes track and remediate newly discovered vulnerabilities
• Performance monitoring identifies potential security-related system issues
• User activity monitoring detects suspicious behavior and policy violations
• Automated alerting systems notify security teams of potential security incidents