How do you secure an API?

APIs are the lifeblood of modern applications—powering mobile apps, connecting microservices, and enabling third-party integrations. But as their importance grows, so does their attractiveness as an attack vector. Securing your APIs isn’t just best practice, it’s essential. And ensuring that security holds up in real-world conditions? That’s where dynamic application security testing (DAST) comes in.

The importance of securing APIs

APIs as primary attack surfaces

APIs expose application logic and data to users—and potentially attackers. Whether REST, SOAP, gRPC, or GraphQL, APIs are increasingly targeted because they’re often overlooked in traditional security testing. They’re also fast-evolving, often changing without a full security audit.

That’s why DAST is critical. It evaluates APIs in their deployed state, simulating attacks to find vulnerabilities that static code scans can miss. DAST doesn’t just theorize about weaknesses—it proves them.

Consequences of poor API security

The stakes are high. API security failures have led to massive data breaches, account hijacking, and unauthorized data access. From leaking personally identifiable information (PII) to allowing full account takeover, the consequences can be severe.

Unfortunately, these issues often go undetected during development or static analysis. Only runtime testing with DAST or manual methods can uncover how APIs behave under real-world attack conditions—before attackers do.

Key components of API security

Authentication

Only verified users or systems should be able to access your API. Methods like OAuth 2.0, JWTs, and mutual TLS are common approaches. DAST tools validate authentication mechanisms by attempting to bypass or exploit them, exposing potential weaknesses.

Authorization

Ensure that users can only access what they’re permitted to. Improper role validation can lead to privilege escalation. DAST simulates unauthorized access to verify whether enforcement is truly working.

Data encryption

Encrypt data in transit with HTTPS and TLS. DAST verifies proper transport layer security and identifies weak ciphers or misconfigurations that put sensitive data at risk.

Rate limiting and throttling

Limit how frequently users can call APIs to prevent abuse or denial-of-service attacks. DAST tools test for rate limit bypasses and excessive request behavior, helping you spot gaps before attackers do.

Input and output validation

Unsanitized inputs can lead to injection vulnerabilities like SQLi or XSS. DAST actively sends malicious payloads to API inputs, testing for weak validation and exposing vulnerable endpoints.

Logging and monitoring

Log every API interaction and monitor for unusual patterns. DAST-generated activity should appear in your logs—if it doesn’t, your visibility might be incomplete.

Step-by-step API security implementation and testing

1. Design with security in mind

Start with secure design principles. Define clear access scopes, input validation rules, and error-handling behavior. But remember: design assumptions must be tested, and DAST verifies them under attack conditions.

2. Use HTTPS and TLS

Never expose APIs over plain HTTP. Enforce TLS and strong cipher suites. DAST tools can check for unsecured endpoints and weak encryption settings.

3. Apply OAuth 2.0 and API key security

API keys offer basic protection, but standards like OAuth 2.0 provide better security through tokens and scopes. DAST tests whether these mechanisms can be bypassed or misused.

4. Set permissions and access controls

Implement role-based or attribute-based access controls to enforce least privilege. DAST simulates access attempts from different privilege levels, revealing over-permissive APIs.

5. Sanitize and validate inputs

Validate all incoming data, especially if it’s used in database queries or passed to other systems. DAST injects test payloads to find vulnerable inputs in live APIs, detecting flaws that code reviews may miss.

6. Monitor and log activity continuously

Use centralized logging, alerting, and analysis to track all API traffic. DAST attacks should be logged clearly; if not, refine your monitoring strategy.

Integrating API security into CI/CD pipelines

In a DevOps world, security testing must shift left—but that won’t be enough to fully secure your APIs. Integrate DAST into your CI/CD pipelines to automatically scan APIs during build and deployment. This ensures real-world security validation alongside static and code-based testing.

Tools like Invicti enable seamless DAST integration into pipelines with support for SOAP, REST, gRPC, and GraphQL APIs. Automate scans, get actionable results, and prevent insecure APIs from reaching production.

Common pitfalls to avoid

Relying on obscurity

Just because an endpoint isn’t documented doesn’t mean it’s inaccessible to attackers. DAST tools use discovery techniques to find undocumented or hidden APIs, highlighting risk areas you may not even know exist.

Hardcoding credentials

Never embed secrets or tokens in front-end code or source control. DAST can detect credentials exposed in error messages, responses, or misconfigured endpoints.

Ignoring rate limiting

APIs without proper rate controls are vulnerable to abuse. This includes not only denial of service (DoS), which is by far the most popular API attack type, but also unlimited data extraction opportunities once another vulnerability is exploited.

Security isn’t set-and-forget—it’s verified with DAST

APIs are everywhere, and though they’re exposed by design, they should not be unprotected. Securing them requires layered defenses, best practices, and constant vigilance. But most importantly, it requires validation.

That’s where DAST plays a vital role: detecting runtime vulnerabilities, testing for real-world threats, and proving whether your API defenses actually work.

If you’re serious about API security, make DAST a core part of your strategy—and integrate it directly into your development pipeline.

Frequently asked questions (FAQ)