Securing APIs: The Overlooked Attack Surface in Cybersecurity

The exponential growth of APIs has transformed how businesses operate, enabling seamless integration, digital transformation, and rapid innovation. However, this expansion has also made APIs a prime target for cyberattacks.

Despite their critical role in modern applications, APIs often remain inadequately protected, exposing organizations to significant risks.

This blog post synthesizes insights from our cybersecurity experts to provide a comprehensive guide to securing APIs.

The Expanding API Attack Surface

APIs now account for 83% of internet traffic, serving as the backbone of web applications, mobile apps, microservices, and cloud-native architectures. Their ubiquity, however, has created a sprawling attack surface:

• Shadow and Zombie APIs: Unmanaged or deprecated APIs often linger in environments, undetected by security teams. Attackers exploit endpoints that organizations don’t even know exist.
• Business Logic Flaws: APIs designed for functionality often lack safeguards against misuse. The 2021 Experian breach, where attackers manipulated unvalidated birthdate fields to access credit histories, exemplifies this risk.
• Hostile Environments: APIs deployed on public clouds face immediate probing. New endpoints on AWS or Azure are scanned and attacked within minutes.

Common Myths and Outdated Practices

Many organizations cling to outdated security assumptions, leaving APIs vulnerable:

• “Firewalls Are Sufficient” – Traditional web application firewalls (WAFs) fail to address API-specific threats such as broken object-level authorization (BOLA) or excessive data exposure.
• “Compliance Equals Security” – Regulatory frameworks like PCI-DSS provide baseline controls but often lag behind evolving threats. APIs need dynamic, risk-based security approaches.
• “We Don’t Have APIs” – Many organizations underestimate their API footprint. If a business has a website, mobile app or cloud integration, it has APIs – whether they realize it or not.

Strategies for Robust API Security

1. Prioritize Visibility and Inventory

• Continuous Discovery: Use runtime traffic analysis and machine learning-driven scanners to identify shadow APIs, misconfigurations, and sensitive data flows. “You can’t secure what you can’t see”
• Risk-Based Tagging: Classify APIs based on data sensitivity and enforce granular security controls.

2. Adopt Zero Trust Principles

• Assume Breach: Shift from perimeter-based security to continuous verification - every API call must be authenticated, authorized, and validated.
• Least Privilege Access: Restrict endpoints to essential functions. Payment APIs, for instance, require stricter monitoring than non-sensitive APIs.

3. Mitigate Top API Threats

• Injection Attacks: SQLi, SSRF, and command injections remain prevalent. Validate and sanitize all inputs, leveraging OpenAPI specs for schema enforcement.
• Credential Stuffing & BOLA: Implement multi-factor authentication (MFA), strict rate limiting, and behavioral analytics. The 23andMe breach, where attackers scraped 6.9 million user profiles via compromised accounts, underscores the need for robust authentication.
• API Leaks: Continuously scan GitHub, Postman, and public repositories for exposed tokens. Secrets stored in plain text are low-hanging fruit for attackers.
• Developer Training: Equip teams to recognize OWASP API Top 10 risks. Interactive labs (e.g., CrAPI, DVGA) provide hands-on exploit practice.

Key Tools and Technologies

• API Gateways: Enforce authentication, rate limiting, and encryption. Gateways are critical to API security but are not a silver bullet.
• Posture Management: Platforms that map API inventories, tag sensitive data, and benchmark security configurations against compliance standards.
• Active Testing: DAST tools (e.g., Burp Suite, Postman) simulate adversarial workflows, while SAST tools audit code for vulnerabilities.

Overcoming Organizational Challenges

• Bridging Silos: Security teams often lack visibility into developer workflows. Collaboration during design reviews and threat modeling prevents costly security gaps.
• Metrics Matter: Track false positives/negatives, incident response times, and API coverage. KPIs like “100% authenticated endpoints” ensure accountability.
• Budget Realities: Prioritize high-risk APIs. Not all endpoints require the same level of scrutiny - focus on crown jewels first.

The Future of API Security

As APIs evolve (GraphQL, gRPC, WebSockets), so do attack vectors. Emerging trends include:

• AI-Powered Defense: Machine leaning models analyze traffic patterns to detect scraping, credential stuffing, and data exfiltration.
• Unified Security Platforms: Converged tools for API discovery, testing, and runtime protection simplify security operations.
• Regulatory Evolution: Compliance frameworks like GDPR, CCPA and industry-specific standards are increasingly mandating API-specific controls.

Key Takeaways

• Inventory All APIs: Continuously discover and classify API endpoints, including legacy and third-party integrations.
• Enforce Zero Trust: Authenticate every request, validate inputs, and apply least-privilege access.
• Test Relentlessly: Combine automated scanning, penetration testing, and red-team exercises.
• Monitor in Real Time: Detect anomalies such as excessive data retrieval or unauthorized privilege escalation.
• Educate Teams: Train developers on secure coding practices and the OWASP API Top 10 risks.