Developer Security Best Practices

1. Authentication & JWT Security

JWT Token Security

JSON Web Tokens (JWTs) are widely used for authentication, but improper handling can lead to serious security vulnerabilities.

JWT Best Practices Implementation

Signature verification should happen on the server. Client-side checks are only for UI hints, not security decisions.

// Good: Server-side JWT verification
// Server
const token = getCookie(req, 'session');
const payload = jwt.verify(token, publicKey);

// Client
fetch('/api/secure', { credentials: 'include' });

// Bad: Trusting tokens without validation
const token = localStorage.getItem('accessToken');
const userData = jwt.decode(token); // No signature verification!

Multi-Factor Authentication (MFA)

Microsoft reports MFA can block 99.9% of account compromise attempts. Implement it wherever possible (Microsoft Security Blog).

• Time-based One-Time Passwords (TOTP) - Apps like Google Authenticator, Authy
• Hardware security keys - YubiKey, Google Titan for highest security
• SMS as last resort - Vulnerable to SIM swapping attacks
• Backup codes - Always provide recovery options

2. Password & Passphrase Management

Why Passphrases Are Superior

Traditional password complexity rules have been proven ineffective. The NIST guidelines now recommend passphrases over complex passwords.

Secure Passphrase Generation

Use cryptographically secure methods to generate passphrases. The ByteTools Passphrase Generatorimplements industry-standard diceware methodology with client-side processing for maximum security.

Password Manager Integration

• Use a reputable password manager - 1Password, Bitwarden, LastPass
• Enable auto-generation - Unique passwords/passphrases for every account
• Secure your master passphrase - This is your single point of failure
• Regular security audits - Check for compromised passwords

3. Data Protection & Privacy

Client-Side vs Server-Side Processing

The location where data processing occurs has significant security implications:

Data Classification and Handling

4. Secure Development Practices

Dependency Security

Dependency vulnerabilities are common and widely tracked in public advisories. Implement these practices and review OWASP guidance on vulnerable components (OWASP A06, GitHub Advisory Database).

• Regular dependency audits - Use npm audit, yarn audit, or pip-audit
• Automated scanning - GitHub Dependabot, Snyk, WhiteSource
• Minimal dependencies - Only include what you actually need
• Pin versions - Use exact versions in production
• Supply chain verification - Verify package signatures when possible

Supply Chain & SBOM

• Generate SBOMs - Use SPDX or CycloneDX formats for dependency transparency
• Provenance & signed releases - Adopt SLSA or Sigstore for build provenance and signing (SLSA, Sigstore)
• Lockfiles & checksums - Commit lockfiles and verify integrity
• Artifact verification - Prefer registries that support integrity metadata
• Secrets scanning - Enable GitHub Secret Scanning or tools like TruffleHog (GitHub Secret Scanning, TruffleHog)
• Pre-commit hooks - Catch secrets before they land in git history (Gitleaks, pre-commit)

Secure Coding Patterns

// Good: Input validation and sanitization
function processUserInput(input) {
  // Validate input
  if (!input || typeof input !== 'string' || input.length > 1000) {
    throw new Error('Invalid input');
  }
  
  // Sanitize input
  const sanitized = input.trim().replace(/[<>]/g, '');
  
  // Process safely
  return sanitized;
}

// Bad: Direct processing without validation
function processUserInput(input) {
  return input.toUpperCase(); // No validation!
}

Environment Security

• Never commit secrets - Use .gitignore for environment files
• Use environment variables - Keep configuration separate from code
• Rotate secrets regularly - API keys, database passwords, certificates
• Principle of least privilege - Grant minimal necessary permissions
• Automate secrets detection - Pre-commit hooks and repository scanning for leaks

5. API & Communication Security

HTTPS Everywhere

All network communication must be encrypted. No exceptions.

• TLS 1.2+ (prefer 1.3) - Disable older, vulnerable protocols
• HSTS headers - Force HTTPS for all connections
• Certificate pinning - Recommended only for mobile/desktop clients you control
• Perfect Forward Secrecy - Use ephemeral key exchange

Note: HPKP is deprecated for web apps. For browsers, rely on modern TLS, HSTS, and certificate transparency instead.

Security Headers & Cookies

• CSP - Reduce XSS risk with strict content policies
• HSTS - Enforce HTTPS at the browser level
• X-Frame-Options - Mitigate clickjacking
• X-Content-Type-Options: nosniff - Prevent MIME sniffing
• Referrer-Policy - Limit referrer leakage
• Permissions-Policy - Disable unneeded browser features
• Cookies - Use HttpOnly, Secure, and SameSite for session cookies

Reference: OWASP Secure Headers Project

API Authentication

Rate Limiting & DDoS Protection

• Implement rate limiting - Per user, per IP, per endpoint
• Use CDN protection - Cloudflare, AWS Shield, Azure Front Door
• Monitor unusual patterns - Automated alerting for anomalies
• Graceful degradation - Maintain core functionality under load

6. Development Tools Security

Choosing Secure Development Tools

The tools you use daily can be security risks if not chosen carefully. Prioritize tools that:

• Process data locally - Client-side processing eliminates data transmission risks
• Have transparent security practices - Open source or clear security documentation
• Don't require account registration - Reduces attack surface and data collection
• Work offline - Independence from network connectivity and servers
• Are regularly updated - Active maintenance and security patches

Tool Verification Checklist

Before using any development tool with sensitive data, verify:

Conclusion

Security is not a destination but a continuous journey. The practices outlined in this guide form the foundation of secure development, but they must be regularly updated as threats evolve and new vulnerabilities are discovered.