Quick answer: An API gateway is the central control layer that sits in front of an organization's APIs and through which all requests pass. It applies authentication, authorization, rate limiting, request validation and monitoring at a single point. From a security standpoint it is a strong opportunity: configured correctly, it provides consistent defense across APIs. But configured wrongly, a single weak point puts all API traffic at risk. API gateway security is hardening this central door itself.

What does an API gateway do?

Modern applications consist of many APIs and microservices. Protecting each one separately is both hard and inconsistent. An API gateway places a single door in front of all these APIs: every incoming request passes through here first, where identity is verified, authorization checked, rate limited and the request validated.

This centralization is a strong security advantage because defense is applied in one place and consistently. But the same centralization also creates a risk affecting all APIs from a single point when the gateway is misconfigured.

API gateway security controls

Control Purpose
Authentication Verifying the identity of each request (token, mTLS)
Authorization Checking the request's permission to that resource
Rate limiting Limiting abuse and DoS
Request validation Schema and input validation, filtering malicious requests
Monitoring and logging Auditable logging of all API traffic
Backend isolation Not exposing the real services directly to the outside

Common mistakes

  • Authorization done only at the gateway, with backend services blindly trusting the gateway (and remaining directly reachable).
  • Missing rate limiting, leaving the API open to abuse and DoS.
  • Services behind the gateway not authenticating separately (internal traffic assumed safe).
  • Sensitive information kept in plaintext in gateway logs.
  • Old and unused API endpoints left open on the gateway.

The KAOS and DSET approach

DSET performs security reviews of the API gateway and the services behind it: is authorization actually applied at every layer, are backend services directly reachable by bypassing the gateway. Our KAOS security engine reports missing authorization checks on API endpoints and directly reachable services that bypass the gateway. In our field experience the most common problem is backend services trusting the gateway and not authenticating on their own. Our goal is to show whether the gateway provides a genuinely consistent defense.

Related reading: API security and OWASP API Top 10, mTLS mutual TLS API security, API rate limiting and bot management, shadow API and API discovery, JWT security and attacks, OAuth 2 and OIDC flow attacks.

Frequently asked questions

Does an API gateway alone keep my APIs secure? No. An API gateway is a strong and consistent defense layer but is not enough on its own. The most common mistake is backend services blindly trusting the gateway, not authenticating on their own, and remaining directly reachable when the gateway is bypassed. The right approach is to use the gateway as central control but also apply identity and authorization at the backend services.

Are an API gateway and a WAF the same? No, they are different but complementary. A WAF filters known web attack patterns. An API gateway applies API lifecycle controls such as authentication, authorization, rate limiting and routing. Many organizations use both together: the gateway manages API logic, the WAF manages attack patterns.

Do backend services behind a gateway need extra protection? Yes. The gateway is a control point, but backend services should not blindly trust it. If an attacker bypasses the gateway or reaches the internal network, services that do not authenticate on their own are left defenseless. Under the zero trust principle, internal traffic should also be verified and services should check identity independently of the gateway.

Sources

For a security review of your API gateway and service architecture, you can talk to our team at Ankara Hacettepe Technopark. Contact DSET.