What Are API Attacks?

What are API attacks?

API attacks are attempts to abuse an application programming interface to read data the caller should not see, change data they should not touch, or exhaust the service so real users cannot use it. They target the endpoints behind web and mobile apps directly, so a flaw that a front end hides is still reachable with a plain HTTP request. Understanding them is the first step of API security. This page is defensive background.

Why attackers go after APIs

• Direct access to data: responses are structured and often come straight from the database.
• Predictable shape: documented routes and sequential IDs are easy to automate against.
• Many entry points: public, partner and internal APIs multiply the surface, and forgotten ones survive (see API discovery).
• No browser in the loop: bots call endpoints without CAPTCHAs or visible pages.

The OWASP API Security Top 10 (2023)

The standard reference is the OWASP API Security Top 10, 2023 edition. Its ten risks, with the defensive idea behind each:

For a plain-language walk through the biggest ones, see top API security risks.

A concrete example

Take BOLA (API1). A logged-in user opens /api/orders/1001 and sees their own order. If the server only checks that the user is logged in, then changing the number to 1002 may return someone else's order. A script can try thousands of IDs in minutes. The fix is not hiding IDs but checking, on every request, that this caller owns this order.

Common mistakes in defending APIs

• Relying on the front end. Hiding a button does not protect the endpoint behind it.
• Authentication without authorization. Knowing who someone is does not decide what they may touch.
• Rate limiting as the only control. It slows abuse (API abuse) but does nothing against BOLA or injection.
• Forgotten versions. An old /v1 without the new checks is a common way in.
• Trusting partner APIs. Treat their responses as untrusted input.

How to detect and reduce API attacks

Layer the controls: authenticate and authorize each request at object and function level, validate input against a schema, return only needed fields, limit rates and sizes per client, keep an inventory of every endpoint and version, and log enough to investigate. Patterns worth alerting on include bursts of 401 and 403 responses, one client walking through sequential IDs, and sudden error or latency spikes. For flooding specifically, see how to stop DDoS attacks and the guide to API rate limiting.

Where monitoring and load testing fit

LoadFocus is not a security scanner and does not find vulnerabilities like injection or BOLA. It helps with the availability side. API monitoring checks endpoints on a schedule (free checks run every 5 minutes) and alerts when status codes, response bodies or response times drift, which can be an early sign that something is hitting the API. Load testing shows how your own API behaves under heavy concurrent traffic, so you can confirm rate limits engage and the service degrades gracefully. Only test systems you own or have permission to test.

FAQ: API Attacks

What is the most common API attack?

OWASP lists Broken Object Level Authorization as API1:2023, the first risk of its Top 10, and it is widely seen because it arises whenever an endpoint trusts an ID without an ownership check.

How are API attacks different from web application attacks?

API attacks target machine-to-machine endpoints that return structured data, with no page or CAPTCHA in between. That makes authorization and input flaws easier to find and automate.

Can a WAF or rate limiter stop them?

They help with floods, known payloads and brute force, but not with logic flaws such as BOLA or business-flow abuse. They work best alongside authorization checks and input validation.

How do I know my API is under attack?

Compare against a baseline: sudden traffic from single clients, rising 401 or 403 rates, sequential ID scanning and latency spikes. Continuous monitoring and alerting make these visible quickly.

Does load testing find security flaws?

No. It measures performance and stability under traffic. It can confirm your rate limits and capacity hold, but a security review or scanner is needed to find vulnerabilities.