Automatic API Attack Tool

Automatic API Attack Tool is a free, open-source utility that turns a Swagger contract into executable API checks. It is best for developers and security teams comfortable maintaining a Java and Gradle project and wanting self-hosted validation and authorization testing. The focused fuzzing is useful for a documented API, but teams without Swagger 2.0 specifications or needing API discovery should choose another approach.

Overview

The tool derives positive and negative request scenarios from declared API parameters. Valid cases stay within the contract's boundaries; negative cases place a randomly invalid value into each checked parameter. This makes the project a practical way to expose weak input handling and unexpected endpoint responses without building every request by hand.

Execution can be incorporated into Jenkins, with jobs started on a schedule or after code pushes. Proxy host and port arguments support routing traffic through an intermediary, which helps fit testing into controlled network environments.

Key features

Contract-driven fuzzing

Swagger 2.0 is mandatory, in either JSON or YAML. Generated values follow the specification for positive scenarios, while each tested parameter can receive a random invalid value for negative coverage. This is well suited to checking validation against a known contract. It is not suitable for discovering undocumented APIs, and teams using a different schema format must convert or replace their specifications.

Extensible attack coverage

The project describes extending request generation and fuzzing for particular requirements, including illegal resource access, cross-site scripting, SQL injection, and remote file inclusion. That flexibility gives security engineers a starting framework rather than a fixed catalog of tests. The breadth of final coverage therefore depends on the scenarios a team implements.

Results and diagnostics

Each run reports request details and whether responses met expected outcomes. TestNG output is written beneath build/testng-results, check details and a summary are printed, and problematic requests are retained in a bad_requests folder. Precise legitimate response codes should be defined for endpoints; otherwise, an overly broad expectation can weaken the usefulness of the results.

Pricing

Automatic API Attack Tool costs nothing under its MIT-licensed open-source plan. The plan includes the complete project, with no seat, usage, or trial term stated. In exchange for the zero license cost, users supply their own Java and Gradle environment, specification, execution infrastructure, and maintenance. This is a strong fit for teams that can operate software internally; organizations seeking vendor-managed operation or packaged support should budget for a different product.

Platforms

The project supports Linux and Windows. Windows builds use gradlew.bat build; on Linux, the documented approach combines a runnable shell script with the JAR to form an executable. Both paths still require Java 8 or newer and Gradle during setup.

Who it's for

Choose it when your API already has a Swagger 2.0 contract and you want repeatable input-validation or authorization checks in a local or Jenkins workflow. It also suits teams that need proxy routing or want to extend scenarios for application-specific attacks. Look elsewhere if your API is described in another format, if you need discovery, or if you prefer a hosted interface that removes build and maintenance work.

Pros and cons

Pros

• Free MIT-licensed code removes licensing cost and permits internal modification.
• Positive and negative cases target both conforming behavior and boundary violations.
• Jenkins scheduling and push triggers support repeatable CI/CD checks.
• TestNG files and preserved bad requests provide artifacts for investigation.
• Proxy arguments and extensible attack logic accommodate controlled, specialized testing.

Cons

• Swagger 2.0 in JSON or YAML is the only supported specification format.
• No API discovery means undocumented services are outside its scope.
• Java, Gradle, and self-hosted build work add operational overhead.
• Response expectations must be defined precisely to keep findings meaningful.

Alternatives

42Crunch API Security Platform is a better choice for a broader platform with OpenAPI auditing, vulnerability scans, and automatic fixes, including a free plan and trial.

OWASP Amass is a free, Apache-licensed framework for teams whose priority is that project rather than specification-driven API attack generation.

APISec Platform fits teams wanting a freemium hosted API testing service with public API testing and basic simulations.

Pynt suits organizations that need a freemium service, with its free tier limited to 10 API endpoints and paid coverage beyond that.

Schemathesis is a free open-source option that generates tests from OpenAPI and GraphQL schemas.

VulnAPI is a free MIT-licensed project for educational and testing use.

WuppieFuzz is a free, open-source REST API fuzzer for teams seeking that specific focus.

AquilaX API Security Scanner is a freemium alternative offering secrets scanning, PII detection, compliance auditing, unlimited scans, and CI/CD and IDE integration on its free plan.

Browse the API Security Testing Software category for more options.

Verdict

Automatic API Attack Tool is a sensible pick for technically capable teams with Swagger 2.0 contracts that want free, repeatable fuzzing inside their own infrastructure. Its main advantage is focused, extensible request generation with useful CI and result artifacts. Look elsewhere when you need API discovery, non-Swagger schemas, or a managed product that avoids Java, Gradle, and ongoing self-hosting work.