Which of the following tools performs comprehensive tests against web servers, including dangerous files and CGIs?

Dsniff is a network sniffing toolkit designed to capture passwords and other sensitive data from network traffic, not to scan web servers for vulnerable files or CGIs.

John the Ripper is a password-cracking tool that performs offline brute-force and dictionary attacks against hashed credentials, and has no web server scanning capability.

Snort is a network intrusion detection and prevention system that monitors and alerts on network traffic, and does not actively probe web servers for dangerous files or CGI vulnerabilities.

Nikto performs comprehensive web server assessments including checks for over 6,700 potentially dangerous files and CGIs, outdated server versions, and version-specific vulnerabilities. It directly targets the web server layer, scanning for known bad files, server configuration issues, and insecure default installations. This makes it the purpose-built tool for the described use case, unlike the other tools which serve entirely different security functions.