_________ is a tool that can hide processes from the process list, can hide files, registry entries, and intercept keystrokes.

A Trojan disguises itself as legitimate software to trick users into executing it, but does not inherently hide processes or intercept OS calls.

Rootkits operate at a low system level (often kernel level) to intercept and modify operating system calls, enabling them to hide malicious processes from the task manager, conceal files from directory listings, mask registry entries, and log keystrokes. Their defining characteristic is stealth - they actively subvert the OS to avoid detection by users and security tools.

A DoS tool is designed to flood a target with traffic or requests to make a service unavailable, not to hide on a system or intercept keystrokes.

A scanner is used to probe networks or systems for open ports and vulnerabilities, not to conceal malicious activity on a compromised host.

A backdoor provides covert unauthorized access to a system but does not inherently hide processes, files, or intercept keystrokes the way a rootkit does.