Hooks are WordPress execution points where custom code can run during normal page or request processing. They come in two main forms: actions, which let code perform work at a specific moment, and filters, which let code modify data before WordPress uses it. This design makes WordPress flexible, but it also gives attackers a reliable place to attach malicious logic without replacing core files.
In real attacks, malware may register a hook through a plugin, theme, must-use plugin, or injected database content so its payload executes on every request, login, or content load. That can help the attacker persist, reload removed backdoors, or hide behavior inside normal site activity. Defenders look for unfamiliar callbacks, suspicious function names, encoded payloads, and hook registrations in files and database rows. Cleaning a site often means removing the malicious code and every hook that still points to it.