Which of the following application security testing techniques is implemented when an automated system generates random input data?

Fuzzing (or fuzz testing) involves using an automated tool to generate large volumes of random, semi-random, or mutation-based input data and submit it to an application under test. The goal is to trigger unexpected behavior, crashes, or security vulnerabilities that structured manual testing would miss, making automated random input generation the defining characteristic of this technique.

XSRF (Cross-Site Request Forgery) is a web attack type where a victim is tricked into submitting an unintended request; it is not a testing methodology involving random input generation.

Hardening refers to the process of reducing an attack surface by disabling unnecessary services and applying security configurations; it is a defensive practice, not an application testing technique.

Input validation is a secure coding defense mechanism that checks and rejects malformed input; it is the countermeasure against attacks, not a testing technique that generates random data.