Architecting Security

Security Architecture

Design and implement comprehensive security architectures that protect systems, data, and users through layered defense strategies, zero trust principles, and risk-based security controls.

Purpose

Security architecture provides the strategic foundation for building resilient, compliant, and trustworthy systems. This skill guides the design of defense-in-depth layers, zero trust implementations, threat modeling methodologies, and mapping to control frameworks (NIST CSF, CIS Controls, ISO 27001).

Unlike tactical security skills (configuring firewalls, implementing authentication, scanning vulnerabilities), security architecture focuses on strategic planning, comprehensive defense strategies, and governance frameworks.

When to Use This Skill

Use security architecture when:

• Designing security for greenfield systems (new applications, cloud migrations)
• Conducting security audits or risk assessments of existing systems
• Implementing zero trust architecture across enterprise environments
• Establishing security governance programs and compliance frameworks
• Threat modeling applications, APIs, or microservices architectures
• Selecting and mapping security controls to regulatory requirements (SOC 2, HIPAA, PCI DSS)
• Designing cloud security architectures (AWS, GCP, Azure multi-account strategies)
• Addressing supply chain security (SLSA framework, SBOM implementation)

Core Security Architecture Principles

1. Defense in Depth

Implement multiple independent layers of security controls so that if one layer fails, others continue to protect critical assets.

9 Defense Layers (2025 Model):

1. Physical Security: Data center access, environmental controls, hardware security modules (HSMs)
2. Network Perimeter: Next-gen firewalls (NGFW), DDoS protection, web application firewalls (WAF)
3. Network Segmentation: VLANs, VPCs, security groups, micro-segmentation
4. Endpoint Protection: EDR, antivirus, device encryption, patch management
5. Application Layer: Secure coding, WAF, API security, SAST/DAST scanning
6. Data Layer: Encryption (at-rest, in-transit, in-use), DLP, backup/recovery
7. Identity & Access Management: MFA, SSO, RBAC/ABAC, privileged access management (PAM)
8. Behavioral Analytics: UEBA, ML-based anomaly detection, threat intelligence
9. Security Operations: SIEM, SOAR, incident response, continuous monitoring

Key Principle: Each layer provides independent protection. Failure of one layer does not compromise the entire system.

For detailed layer-by-layer implementation patterns, see references/defense-in-depth.md.

2. Zero Trust Architecture

Implement "never trust, always verify" principles where every access request is authenticated, authorized, and continuously validated.

Core Zero Trust Principles:

1. Continuous Verification: Authenticate and authorize every access request (no implicit trust)
2. Least Privilege Access: Grant minimal permissions required, use just-in-time (JIT) access
3. Assume Breach: Design systems expecting compromise, limit blast radius
4. Explicit Verification: Verify user identity (MFA), device health, application integrity, context (location, time, behavior)
5. Micro-Segmentation: Divide networks into small isolated zones, control east-west traffic

Zero Trust Architecture Components:

• Policy Engine: Centralized authorization decision point (allow/deny)
• Identity Provider (IdP): User/machine identity verification (Azure AD, Okta)
• Device Posture Service: Device health checks (MDM, EDR integration)
• Context/Risk Engine: Behavioral analytics, location, time, threat intelligence
• Policy Enforcement Points: Gateways enforcing decisions (ZTNA, API gateways)

For zero trust implementation roadmap and reference architecture, see references/zero-trust-architecture.md.

3. Threat Modeling

Systematically identify, prioritize, and mitigate security threats through structured methodologies.

Primary Methodologies:

STRIDE Threat Categories:

• Spoofing: Attacker impersonates another user/system (Mitigation: MFA, certificate validation)
• Tampering: Unauthorized data modification (Mitigation: Encryption, digital signatures)
• Repudiation: User denies action without proof (Mitigation: Audit logs, non-repudiation)
• Information Disclosure: Confidential data exposure (Mitigation: Encryption, access controls, DLP)
• Denial of Service: System unavailability (Mitigation: Rate limiting, DDoS protection, redundancy)
• Elevation of Privilege: Gaining higher privileges (Mitigation: Least privilege, input validation, patching)

STRIDE Application Process:

1. Model the system using data flow diagrams (DFDs)
2. Identify threats by applying STRIDE to each component/data flow
3. Document threats with STRIDE categories
4. Prioritize threats using DREAD scoring or business impact
5. Design mitigation controls

For detailed threat modeling methodologies, PASTA process, DREAD scoring, and attack trees, see references/threat-modeling.md. For threat modeling examples, see examples/threat-models/.

Security Control Frameworks

Map security controls to industry frameworks to ensure comprehensive coverage and compliance.

NIST Cybersecurity Framework (CSF) 2.0

6 Core Functions:

1. GOVERN (GV): Risk management strategy, policies, supply chain risk management
2. IDENTIFY (ID): Asset inventory, risk assessment, continuous improvement
3. PROTECT (PR): Access control, data security, platform security, infrastructure resilience
4. DETECT (DE): Continuous monitoring, anomaly detection, security event analysis
5. RESPOND (RS): Incident management, analysis, communication, mitigation
6. RECOVER (RC): Recovery planning, execution, post-incident improvement

Usage: Map security controls to NIST CSF categories to ensure coverage of all security functions. Provides risk-based, flexible framework for security programs.

For detailed NIST CSF category mapping and subcategories, see references/nist-csf-mapping.md.

CIS Critical Security Controls v8

18 Controls organized in 3 Implementation Groups:

• IG1 (Basic): 56 safeguards for small organizations (asset inventory, access control, logging, backups)
• IG2 (Intermediate): +74 safeguards for mid-sized organizations with IT security staff
• IG3 (Advanced): +23 safeguards for large enterprises with dedicated security teams

Top Priority Controls (IG1):

1. Inventory and Control of Enterprise Assets
2. Inventory and Control of Software Assets
3. Data Protection
4. Secure Configuration of Enterprise Assets
5. Account Management
6. Access Control Management
7. Continuous Vulnerability Management
8. Audit Log Management

Usage: CIS Controls provide prescriptive, measurable security baseline. Start with IG1, progress to IG2/IG3 as security maturity increases.

For detailed CIS Controls implementation guidance, see references/cis-controls.md.

OWASP Top 10 Risk Mitigation

Map OWASP Top 10 application security risks to architectural controls:

For detailed OWASP Top 10 mitigation strategies and code examples, see references/owasp-top10-mitigation.md.

Architecture Selection Decision Framework

Select appropriate security architecture approach based on system characteristics:

Greenfield (New System):

• Implement Zero Trust from Day 1
• Identity-first architecture (MFA, SSO, RBAC/ABAC)
• Micro-segmentation by default
• Assume breach mentality (limit blast radius)
• Continuous verification and monitoring

Brownfield (Existing System):

• Hybrid: Maintain Defense in Depth + Zero Trust overlay
• Keep existing perimeter controls (firewalls, VPN)
• Layer Zero Trust controls progressively
• Segment critical assets first (data, admin access)
• Modernize identity and access management

Compliance-Driven:

• Map to control frameworks based on requirements:
  • General Security: NIST CSF for risk-based approach
  • Baseline Hardening: CIS Controls for prescriptive guidance
  • Comprehensive ISMS: ISO 27001 for certification
  • Industry-Specific: PCI DSS (payments), HIPAA Security Rule (healthcare), FedRAMP (government)

Cloud-Native:

• Use cloud provider reference architectures:
  • AWS: Well-Architected Framework (Security Pillar)
  • GCP: Security Best Practices, Security Command Center
  • Azure: Security Benchmark, Defender for Cloud
• Implement cloud-native security services (CSPM, CWPP)

Hybrid/Multi-Cloud:

• Cloud Security Posture Management (CSPM) for unified policy enforcement
• Cross-cloud visibility and monitoring
• Cloud-agnostic IAM (Okta, Azure AD)

For detailed architecture selection decision trees, see references/defense-in-depth.md and references/zero-trust-architecture.md.

Supply Chain Security

Protect software supply chain from tampering, backdoors, and compromised dependencies.

SLSA Framework

Supply-chain Levels for Software Artifacts (4 levels):

1. SLSA Level 1 - Provenance: Build process generates provenance metadata (not tamper-proof)
2. SLSA Level 2 - Hosted Build: Build on trusted platform (GitHub Actions, Cloud Build)
3. SLSA Level 3 - Hardened Build: Build platform prevents tampering, audit logs
4. SLSA Level 4 - Hermetic, Reproducible: Fully hermetic builds, reproducible, two-party review

Implementation: Start with Level 1 provenance generation, progress to Level 2 (GitHub Actions), then Level 3 (hardened CI/CD with audit logs).

SBOM (Software Bill of Materials)

Generate and maintain inventory of software components and dependencies.

SBOM Standards:

• CycloneDX: OWASP standard (JSON/XML format)
• SPDX: Linux Foundation standard
• SWID: ISO/IEC 19770-2 standard

SBOM Use Cases:

• Vulnerability Management: Quickly identify affected components during CVE disclosures
• License Compliance: Track open-source licenses for legal compliance
• Supply Chain Risk: Visibility into third-party code and dependencies
• Incident Response: Rapid assessment of Log4Shell-type incidents

Dependency Management Best Practices:

1. Generate SBOM automatically in CI/CD pipeline
2. Continuous scanning with tools (Dependabot, Snyk, Trivy, Grype)
3. Automated security patch updates
4. License compliance tracking and approval workflows
5. Pin dependency versions using lock files
6. Minimize dependencies to reduce attack surface

For SLSA implementation guide, SBOM generation examples, and dependency scanning automation, see references/supply-chain-security.md.

Cloud Security Architecture Patterns

AWS Security Architecture

Well-Architected Framework - Security Pillar Principles:

1. Strong identity foundation: Centralize IAM, least privilege, IAM Identity Center (SSO)
2. Enable traceability: CloudTrail, GuardDuty, Security Hub for comprehensive logging
3. Apply security at all layers: Defense in depth across VPC, instances, applications, data
4. Automate security best practices: Infrastructure as Code (Terraform, CloudFormation)
5. Protect data in transit and at rest: TLS 1.3, AWS KMS, encryption everywhere

Key AWS Security Services:

• IAM: AWS IAM, IAM Identity Center (SSO), Cognito (customer identity)
• Detection: GuardDuty (threat detection), Security Hub (centralized findings), Detective (investigation)
• Network: AWS WAF, Shield (DDoS), Network Firewall
• Data: KMS (key management), Secrets Manager, Macie (data classification)
• Compute: Systems Manager (patch management), Inspector (vulnerability scanning)

Multi-Account Strategy: Use AWS Organizations with Security OU (Security Account, Logging Account, Audit Account) and Workload OUs (Production, Non-Production). Apply Service Control Policies (SCPs) for guardrails.

For AWS reference architectures and multi-account security setup, see references/aws-security-architecture.md and examples/architectures/aws-multi-account-security.md.

GCP Security Architecture

Key GCP Security Services:

• IAM: Cloud IAM, Identity Platform (customer identity), Cloud Identity (workforce)
• Detection: Security Command Center (unified dashboard), Chronicle (SIEM), Event Threat Detection
• Network: Cloud Armor (DDoS/WAF), VPC Service Controls (data exfiltration prevention), Cloud Firewall
• Data: Cloud KMS, Secret Manager, Cloud DLP (data loss prevention)
• Compute: Binary Authorization (image signing), Confidential Computing (encryption in use)

Organization Hierarchy: Structure with Organization → Folders (Production, Non-Production, Security) → Projects. Apply IAM policies at folder level for inheritance.

For GCP security architecture patterns and organization setup, see references/gcp-security-architecture.md and examples/architectures/gcp-security-hierarchy.md.