Web applications are increasingly popular targets for cybercriminals due to the rich data they hold, access into backend systems, and use as infrastructure for further attacks. According to statistics, around 90% of web apps have exploitable vulnerabilities, whether custom-built or using common platforms like WordPress or Django.
While tools like web application firewalls can offer some protection, properly securing web apps requires a multi-layered approach involving:
1. Rigorous design guidelines
2. Secure development practices
3. Robust defensive coding
Design Guidelines
A major source of vulnerabilities stems from insecure design architecture and bad security development lifecycle practices. Some best practices include:
- Minimal attack surface area: Restrict accessible endpoints, disable unused features/pages, implement judicious use of permissions and access controls
- Avoid security misconfigurations: Harden web servers, frameworks, libraries, APIs, and all components
- Validate all inputs: Scrub user input for injection attacks, allowlist expected types
- Principle of least privilege: Grant minimal necessary access across users, services, and 3rd party integrations
- Encrypt sensitive data: Properly handle credentials, tokens, and API keys using cryptographic best practices
- Fail safely: Handle errors securely, avoid exceptions and stack trace leakage
Secure Development Practices
While good design sets the security foundation, development practices must also follow secure SDLC principles including:
- Developer awareness training: Keep developers informed on leading threats like injection attacks, misconfigurations, input validation
- Reference secure code samples: Establish reusable security controls for authentication, encryption, and input validation rather than rely on developers to implement securely on their own
- Peer review all code changes: Require peer signoff to detect potential flaws early before release
- Static analysis security testing (SAST): Scan source code in the pipeline to catch high-risk coding issues
- Repository isolation: Protect source code from unauthorized access
- Integrate security into agile processes: Include security user stories in sprints, prioritize threats through risk analysis
Robust Defensive Coding
In addition to secure design and development, in-line defensive coding serves as another barrier against exploitation:
- Parameterize queries: Use prepared statements with bind variables rather than concatenated SQL which enables SQL injection
- XML external entity (XXE) protection: Configure XML parsers securely to prevent XXE attacks
- Implement CSRF tokens: Protect state changing requests from cross site forgery
- Allowlist inputs: Validate all input data types, length, format and range
- Output encoding: Encode untrusted output sourced from databases or users before rendering to prevent XSS
- Disable error handling that reveals system details: Don't leak stack traces and debug data to users
Comprehensive Testing
Finally, rigorously testing web apps for vulnerabilities through manual penetration testing augmented by DAST scanning provides another crucial layer of protection:
- Input fuzzing: Test expected and unexpected inputs through manual and automated data mutation
- Authentication & access controls testing: Verify all authn/authz controls, test account roles/privileges
- Logic testing: Check workflow inconsistencies, race conditions, error handling
- Configuration review: Inspect systems, frameworks and apps for common misconfigurations
- Encryption validation: Confirm proper implementation of all encryption, hashing, key handling
- Session management: Ensure session tokens and management is secure against fixation, hijacks & replay
- API testing: Fuzz and penetration test all API interfaces exposed
- File uploads: Check for restriction of types, content scanning, path traversal issues
- HTML, JavaScript inspection: Manually analyze client-side code for weaknesses
- Automated scans: Run the latest DAST scans frequently using both black-box and authenticated analysis
Conclusion
With web apps becoming the new endpoint - full of valuable data, credentials, and access potential - securing them has become mission-critical. Organizations can make apps substantially more secure and resilient to attack by combining secure design principles, developer best practices, defensive coding, and comprehensive testing. The guidelines provided above can serve as a starting point for establishing an application security program capable of scaling across the organization. Adhering to these will lead to more secure code being pushed to production and fewer critical application vulnerabilities for attackers to exploit.
