APIs (Application Programming Interfaces) are the lifeblood of modern digital ecosystems. They enable seamless connectivity between systems, applications, and services. However, with increased adoption comes increased risk. APIs are a prime target for cyber attackers because they often expose sensitive data and business logic.

According to the 2024 State of API Security Report by Salt Security, the exponential growth in API traffic has significantly widened organisations' attack surfaces. Alarmingly, 37% of respondents reported experiencing an API security incident in the past 12 months, more than doubling the 17% recorded in 2023. This stark increase highlights that API security is no longer merely an IT operational concern; it has become a core business risk that demands executive-level attention.

In this article, we will explore the most common types of API attacks, examine why these threats are on the rise, outline the potential consequences and challenges, and provide key strategies you can implement to safeguard your APIs.

Understanding the API Threat Landscape

1. Types of API Attacks

Before implementing defences, it is important to understand the most prevalent API attack vectors:

• Injection Attacks: SQL, NoSQL, and command injections can compromise backend systems if user inputs are not properly sanitised.
• Broken Authentication: Weak or improperly implemented authentication mechanisms allow attackers to assume other users' identities.
• Excessive Data Exposure: APIs that return more data than necessary provide attackers with more information to exploit.
• Lack of Rate Limiting: Without throttling, APIs are vulnerable to brute force attacks and denial-of-service (DoS) attacks.
• Improper Asset Management: Forgotten endpoints, shadow APIs, and deprecated versions expose vulnerabilities.
• Security Misconfiguration: Default settings and poor security controls leave APIs wide open to exploitation.

2. Consequences of API Attacks

API attacks can result in devastating consequences for organisations:

• Data Breaches: Exposure of sensitive customer or internal data.
• Service Downtime: Leading to operational disruption and revenue loss.
• Reputational Damage: Loss of customer trust and brand reputation.
• Regulatory Fines: For non-compliance with data protection laws like GDPR or HIPAA.
• Intellectual Property Theft: Competitors or malicious actors gaining access to proprietary systems and processes.

3. Why API Security Incidences are Becoming More Common

Several factors have contributed to the surge in API security incidents:

• Proliferation of APIs: Modern applications often depend on dozens or hundreds of internal and external APIs.
• Rapid Development Cycles: Agile and DevOps practices sometimes prioritise speed over security.
• Complex Ecosystems: Hybrid and Multi-Cloud environments introduce integration challenges and blind spots.
• Increasing Sophistication of Attackers: Cybercriminals are becoming more skilled at discovering and exploiting API vulnerabilities.

4. The Challenges with Securing APIs

Despite growing awareness, securing APIs remains a complex task due to:

• Visibility Issues: Lack of comprehensive inventories and documentation for all deployed APIs.
• Authentication Complexity: Managing secure authentication across a diverse API landscape.
• Inconsistent Security Standards: Differing protocols, platforms, and technologies lead to fragmented security controls.
• Third-Party Risks: Integrations with external APIs can introduce vulnerabilities outside the organisation's direct control.

Best Practices for Securing APIs

1. Enforce Strong Authentication and Authorisation

Implement authentication protocols such as OAuth 2.0 or OpenID Connect. APIs should use token-based authentication and validate all tokens rigorously.

Example: Using JumpCloud for identity management can centralise authentication and enforce multi-factor authentication (MFA) for API access.

Additionally, enforce the principle of least privilege with scoped access tokens, ensuring users and applications only have access to what they need.

2. Implement Input Validation & Output Encoding

Never trust client input. Use strong server-side validation to sanitise all incoming data. Apply allow-lists (whitelists) where possible and reject unexpected inputs.

Output encoding reduces the risk of execution by ensuring that potentially malicious input is rendered as inert text rather than executable code in client-side contexts like HTML or JavaScript. However, it should not be relied on as the sole defence - robust input validation and contextual sanitisation are still essential, as skilled attackers may attempt to bypass encoding schemes.

3. Protect APIs with Rate Limiting & Throttling

To prevent abuse and brute-force attacks, apply rate limiting per IP, per user, and per token.

For example, integrating Cloudflare can help manage API security with automatic rate limiting and bot mitigation features.

Tip: Design APIs to gracefully handle rate limit breaches by responding with HTTP 429 Too Many Requests.

4. Encrypt Data in Transit & at Rest

Use HTTPS/TLS to secure all data in transit. Configure servers to enforce strict security headers like Strict-Transport-Security (HSTS), Content-Security-Policy (CSP), and disable older, vulnerable protocols.

For data at rest, leverage encryption solutions offered by cloud providers such as Google Cloud Platform (GCP) and AWS, ensuring end-to-end protection.

5. Conduct Regular API Security Assessments

API security isn’t a "set it and forget it" activity. Conduct regular Cloud Security Assessments to identify vulnerabilities, configuration drifts, and new threats.

Penetration testing focusing specifically on APIs helps simulate real-world attack scenarios and uncover flaws before malicious actors do.

6. Secure API Gateways & Use Micro-Segmentation

An API gateway acts as a security barrier that routes, authenticates, and filters API traffic.

Best Practice: Implement micro-segmentation behind the API Gateway. Use service meshes like Istio or Consul for service-to-service authentication and authorisation.

Using Hashicorp Consul for service mesh can greatly enhance API security by managing service discovery and secure communication using mTLS.

7. Monitor & Audit API Activity

Real-time monitoring, logging, and alerting are critical for detecting and responding to threats. Tools like Datadog and Elastic can ingest API logs, provide observability, and detect anomalies.

Key Metrics to Monitor:

• Unusual API usage patterns
• Frequent failed authentication attempts
• Rate limit breaches
• Sensitive data exposure events

8. Adopt a Zero Trust Security Model

In a Zero Trust model, every request to the API is assumed to be untrustworthy until proven otherwise.

• Authenticate and authorise every request.
• Use short-lived tokens.
• Revalidate sessions frequently.

When implemented correctly, Zero Trust architecture significantly reduces the blast radius of a breach.

Bonus: Secure Your API Supply Chain

With the rise of microservices, API aggregations, and third-party integrations, the API supply chain is increasingly complex - and a growing target for attackers. Each dependency, third-party library, or partner integration introduces potential vulnerabilities that can cascade through your systems if not properly governed.

Best Practices for Securing the API Supply Chain:

• Vetting Dependencies: Conduct rigorous reviews of third-party APIs and libraries. Evaluate their security practices, update frequency, and known vulnerabilities.
• Contractual Security Requirements: Ensure SLAs and integration contracts explicitly state security obligations, including encryption, authentication, and incident response expectations.
• Audit and Inventory: Regularly audit your software bill of materials (SBOM) to maintain visibility over all direct and transitive dependencies.

Leverage DevSecOps Maturity Frameworks:

• SLSA (Supply-chain Levels for Software Artifacts) provides a security framework for verifying the integrity of software artifacts. Following SLSA can help prevent tampering and enforce build provenance.
• OWASP DSOMM helps teams assess and improve their DevSecOps capabilities, ensuring security is embedded from code to deployment.

Tools That Help Achieve SLSA Compliance:

Cloud-native CI/CD tools can significantly simplify compliance with frameworks like SLSA:

• Cloud Build: GCP’s serverless CI/CD platform supports build provenance tracking, a key requirement for SLSA Level 2+.
• Binary Authorisation: Ensures only trusted and verified images are deployed to production by enforcing deploy-time policy controls.

Example Implementation:

Using GitLab for CI/CD integrated with Google Cloud’s Cloud Build and Binary Authorization enables a robust, end-to-end secure pipeline. It allows you to:

• Scan dependencies automatically during builds.
• Sign and verify artifacts.
• Restrict deployments to cryptographically verified images.

By embedding security controls directly into your software factory, you reduce the attack surface and strengthen trust in your API infrastructure.

Conclusion

APIs are indispensable in today's cloud-native world, but without strong security practices, they become significant liabilities. By enforcing layered security controls, regularly assessing your API security posture, and leveraging advanced tooling, organisations can dramatically reduce their risk exposure.

For those embarking on a broader API security initiative or facing complex cloud environments, a thorough Cloud Security Architecture design is highly recommended.

Need expert help securing your APIs or cloud environments? Click here to get in touch with Deimos today.

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API FAQs

1. What are API attacks?

API attacks are malicious attempts to exploit vulnerabilities in an API to gain unauthorised access, disrupt services, or steal sensitive data.

2. What is an API breach?

An API breach occurs when attackers successfully exploit an API vulnerability to gain unauthorised access to data, systems, or services.

3. What is an API in cyber security?

In cyber security, an API is an interface that allows software applications to communicate with each other. Protecting APIs is critical because they often expose sensitive data and functionality.

4. What are some common types of API attacks?

Common API attacks include Injection attacks, Broken Authentication, Excessive Data Exposure, Distributed Denial-of-Service (DDoS) attacks, Man-in-the-Middle (MITM) attacks, and Security Misconfigurations.

5. What are the potential consequences of API attacks?

API attacks can result in data breaches, service downtime, financial loss, reputational damage, regulatory fines, and intellectual property theft.

6. What is API security?

API security refers to the practices and tools used to prevent attacks, ensure the confidentiality and integrity of data, and authenticate legitimate users interacting with APIs.

7. How often should API security assessments be performed?

Ideally, API security assessments should be performed quarterly or whenever significant changes are made to the APIs or their infrastructure.

8. Is using HTTPS enough to secure APIs?

HTTPS is essential, but it's only one part of a comprehensive security strategy. Authentication, input validation, monitoring, and rate limiting are equally critical.

9. How do I protect APIs from DDoS attacks?

Implementing rate limiting, leveraging CDN and WAF solutions like Cloudflare, and having scalable infrastructure can mitigate DDoS attacks.