Introduction: Security as a Developer Responsibility
Security breaches make headlines regularly, and the consequences—data exposure, financial loss, reputational damage—are severe. While security teams provide expertise, every developer shares responsibility for building secure systems. Vulnerabilities often originate in code, making secure coding practices essential.
At TetraNeurons, security is embedded in our development process. From handling sensitive agricultural data in Agrilanka to managing emergency information in our disaster management application, we take security seriously. This guide covers fundamentals every developer should know.
The OWASP Top 10: Common Vulnerabilities
The OWASP Top 10 lists the most critical web application security risks. Understanding these vulnerabilities—and how to prevent them—provides a foundation for secure development.
Injection attacks occur when untrusted data is sent to interpreters. SQL injection remains prevalent despite being well-understood. The solution: parameterized queries that separate code from data. Never concatenate user input into queries.
Broken authentication allows attackers to compromise user accounts. Implement proper session management, protect against credential stuffing with rate limiting, use secure password hashing (bcrypt, Argon2), and offer multi-factor authentication.
Sensitive data exposure happens when applications don't adequately protect data. Encrypt data in transit (TLS) and at rest. Don't store sensitive data you don't need. Implement proper key management.
Input Validation: Trust Nothing
All input from external sources—users, APIs, files, databases—must be validated. Assume it's malicious until proven otherwise. This defensive mindset prevents many vulnerability classes.
Validate on the server side. Client-side validation improves user experience but provides no security—attackers bypass it trivially. Server-side validation is the actual security control.
Use allowlists over denylists. Defining what's allowed is more robust than trying to block everything dangerous. A field expecting a number should accept only digits, not try to filter out dangerous characters.
Validate type, length, format, and range. An email field should look like an email and have reasonable length. A date field should parse as a valid date within acceptable range. Reject invalid input early.
Output Encoding: Preventing Injection
Output encoding prevents injection into different contexts. The right encoding depends on where data appears—HTML, JavaScript, CSS, URLs, SQL queries each require different encoding.
For HTML contexts, encode special characters (<, >, &, ", ') to prevent XSS. Most frameworks provide auto-encoding in templates. Ensure it's enabled and avoid bypassing it.
For JavaScript contexts, JSON encoding prevents injection. Never interpolate user data directly into script blocks. Pass data through JSON serialization or data attributes.
For URLs, encode user data with proper URL encoding. For SQL, use parameterized queries (not encoding). Match the encoding to the context.
Authentication: Verifying Identity
Authentication verifies users are who they claim to be. Getting it wrong has severe consequences—unauthorized access to accounts and data.
Password storage requires proper hashing. Use bcrypt, scrypt, or Argon2—algorithms designed for password hashing with configurable work factors. Never use MD5, SHA-1, or even SHA-256 alone. Never store plaintext passwords.
Implement account lockout after failed attempts, but balance security against denial of service. Temporary lockouts with increasing delays provide reasonable protection. CAPTCHA can supplement for high-risk operations.
Multi-factor authentication adds significant security. TOTP (time-based one-time passwords), hardware keys, or push notifications require attackers to compromise multiple factors.
Authorization: Enforcing Access Control
Authorization determines what authenticated users can do. Even authenticated users shouldn't access everything—principle of least privilege applies.
Check authorization on every request. Don't rely on hiding UI elements—attackers can call APIs directly. Server-side authorization checks are required for every sensitive operation.
Implement proper access control models. Role-based access control (RBAC) assigns permissions to roles, then roles to users. Attribute-based access control (ABAC) enables more fine-grained decisions based on user, resource, and context attributes.
Test authorization thoroughly. Can users access other users' data by changing IDs? Can they perform actions their role shouldn't allow? These tests should be automated.
Session Management: Maintaining State Securely
Sessions track authenticated state across requests. Session vulnerabilities enable account takeover even without credentials.
Generate session IDs with cryptographic randomness. Predictable IDs enable session prediction attacks. Use framework-provided session management rather than building your own.
Protect session IDs in transit. Use secure, httpOnly cookies. Set the secure flag for HTTPS-only transmission. Consider SameSite attribute for CSRF protection.
Implement proper session lifecycle. Expire sessions after inactivity. Allow users to terminate sessions. Regenerate session ID after authentication to prevent fixation attacks.
Cryptography: Protecting Data
Cryptography protects data confidentiality and integrity. Using it correctly requires understanding its principles and limitations.
Use established algorithms and libraries. AES for symmetric encryption, RSA or ECC for asymmetric, SHA-256 or SHA-3 for hashing. Don't invent cryptographic schemes. Don't implement algorithms yourself—use vetted libraries.
Key management is often harder than encryption itself. Generate keys with proper randomness. Store keys securely (key management services, HSMs). Rotate keys periodically. Plan for key compromise scenarios.
Understand what cryptography provides. Encryption provides confidentiality. Hashing provides integrity verification. Signatures provide authentication and non-repudiation. Choose appropriate tools for your security goals.
API Security: Protecting Interfaces
APIs expose application functionality and are prime attack targets. API security requires attention to authentication, authorization, input validation, and rate limiting.
Authenticate API requests appropriately. API keys for service-to-service calls. OAuth tokens for user-authorized access. JWTs need proper validation—verify signatures, check expiration, validate claims.
Rate limiting prevents abuse. Limit requests per user, per IP, per endpoint as appropriate. Return proper status codes (429 Too Many Requests) with retry-after headers.
Validate all API input. Define schemas and reject non-conforming requests. Be especially careful with batch operations and nested objects that might bypass simple validation.
Dependencies: Managing Supply Chain Risk
Modern applications depend on thousands of packages. Vulnerabilities in dependencies become your vulnerabilities. Supply chain attacks inject malicious code into legitimate packages.
Audit dependencies regularly. Tools like npm audit, Snyk, and Dependabot identify known vulnerabilities. Update vulnerable packages promptly. Track security advisories for critical dependencies.
Minimize dependencies. Each dependency is a potential vulnerability. Evaluate whether you really need a package. Sometimes implementing simple functionality is safer than adding dependencies.
Use lockfiles to ensure reproducible builds. Verify package integrity through checksums. Consider using private registries or vendoring critical dependencies for additional control.
Logging and Monitoring: Detecting Attacks
Security logging enables detecting attacks and investigating incidents. Log security-relevant events: authentication attempts, authorization failures, input validation failures, errors.
Don't log sensitive data. Passwords, tokens, personal information shouldn't appear in logs. Mask or omit sensitive fields. Review log output to ensure nothing sensitive leaks.
Monitor for anomalies. Unusual login patterns, spikes in failed requests, unexpected geographic access might indicate attacks. Set up alerts for suspicious patterns.
Protect logs themselves. Attackers often try to delete or modify logs to cover tracks. Store logs securely, with integrity protection, in separate systems attackers can't easily access.
Security Testing: Finding Vulnerabilities
Multiple testing approaches find different vulnerability types. A comprehensive security testing strategy combines several methods.
Static analysis (SAST) examines code without execution. Tools identify potential vulnerabilities—SQL injection, XSS, insecure configurations—in source code. Integrate into CI pipelines for continuous checking.
Dynamic analysis (DAST) tests running applications. Tools probe for vulnerabilities by sending malicious inputs and analyzing responses. Run against staging environments to find issues before production.
Penetration testing employs human expertise to find vulnerabilities automated tools miss. Regular pen tests by qualified professionals provide realistic assessment of security posture.
Incident Response: Preparing for Breaches
Despite best efforts, breaches happen. Incident response plans ensure you can detect, contain, and recover from security incidents effectively.
Have a plan before you need it. Define roles, communication channels, escalation procedures. Practice with tabletop exercises. Know how to contact relevant parties—security team, legal, communications.
Detection enables response. Security monitoring, anomaly detection, and user reports all contribute. The faster you detect incidents, the faster you can respond.
Learn from incidents. Post-incident reviews identify what happened, why, and how to prevent recurrence. Document lessons learned. Update defenses and processes accordingly.
Conclusion: Security as Practice
Security isn't a feature you add—it's a practice you follow. Secure development requires ongoing attention, continuous learning, and constant vigilance. Threats evolve, requiring defenses to evolve too.
At TetraNeurons, security awareness pervades our development culture. We train continuously, review code for security, test thoroughly, and respond to issues promptly. This investment protects our users and our reputation.
Start with fundamentals: input validation, output encoding, proper authentication. Build security into your development process. Stay informed about emerging threats. Security is everyone's responsibility, and these fundamentals provide a strong foundation for building systems users can trust.