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🔐 Secure System Design: A Quick Guide

Designing secure systems requires a comprehensive approach that spans users, infrastructure, applications, APIs, and operations. This guide introduces key security areas and how to address them effectively.

🔑 1. Authentication

Authentication verifies who the user is.

Use strong, modern mechanisms like:
- OAuth 2.0 / OpenID Connect
- MFA (Multi-Factor Authentication)
- SSO (Single Sign-On)
Store passwords securely with salted hashes (e.g., bcrypt, argon2)
Support secure session management with token expiration and revocation

🛂 2. Authorization

Authorization defines what authenticated users can access.

Apply Role-Based Access Control (RBAC) or Attribute-Based Access Control (ABAC)
Use principle of least privilege: grant only the necessary permissions
Enforce authorization on every request, including internal microservices

🔒 3. Encryption

Encryption protects data at rest and in transit.

In Transit: Use TLS 1.2+ for all communications
At Rest: Encrypt data using AES-256 or similar
Use key management systems (KMS) like AWS KMS, HashiCorp Vault
Avoid hardcoding keys in codebases

🐞 4. Vulnerability Management

Find and fix security flaws proactively.

Perform regular code scanning and dependency auditing
Use tools like Snyk, Dependabot, Trivy, or OWASP ZAP
Patch systems and third-party dependencies regularly
Follow OWASP Top 10 to address common risks

📜 5. Audit & Compliance

Ensure you can trace and prove secure behavior.

Enable audit logging for critical actions (logins, config changes)
Retain logs with immutability and retention policies
Prepare for compliance frameworks like GDPR, HIPAA, SOC2

🌐 6. Network Security

Protect the network perimeter and internal communication.

Use firewalls, WAFs (Web Application Firewalls), and NAT gateways
Segment networks (e.g., DMZ, internal-only zones)
Block unused ports and protocols
Apply Zero Trust principles for internal services

💻 7. Terminal Security

Secure access to production systems.

Use SSH key-based authentication with expiration and rotation
Enforce MFA for bastion access
Implement Just-in-Time (JIT) access and session recording
Disable root login and restrict sudo privileges

🚨 8. Emergency Responses

Prepare for incidents and threats.

Define an incident response plan (IRP)
Set up alerting for suspicious behavior
Conduct tabletop exercises and post-mortems
Use tools like SIEM, IDS/IPS for detection and response

📦 9. Container Security

Secure containerized environments like Docker or Kubernetes.

Scan images for vulnerabilities before deployment
Use read-only containers, non-root users, and resource limits
Apply PodSecurityPolicies / Security Contexts
Keep orchestrators (like Kubernetes) updated

🧩 10. API Security

Protect internal and external APIs.

Require authentication and authorization for all endpoints
Validate input to avoid injection attacks (SQLi, XSS)
Use rate limiting, throttling, and API keys
Log usage for monitoring and abuse detection

🧾 11. 3rd-Party Vendor Management

Secure your dependencies and partnerships.

Evaluate vendor security posture (SOC2, ISO certifications)
Use contracts and SLAs that include security responsibilities
Perform regular assessments and limit access to necessary scopes

🌪 12. Disaster Recovery

Plan for major outages and data loss.

Implement automated backups and test restore procedures
Use geo-redundant infrastructure for high availability
Define Recovery Time Objective (RTO) and Recovery Point Objective (RPO)
Regularly simulate disaster recovery drills

🧠 Final Checklist

✅ Use secure defaults and fail closed
✅ Apply defense in depth across layers
✅ Automate security scanning and patching
✅ Educate the engineering team on secure practices

📚 Resources

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