Nikto is a popular webserver assessment tool that scans for over 6700 potentially dangerous files and programs, checks for outdated server versions of over 1250 servers, and identifies version-specific problems on 270+ servers. It identifies vulnerabilities very quickly but is not stealthy, making the scans obvious in server logs. Nikto allows tuning scans to specific categories like file uploads, information disclosure, or SQL injection, and has features like SSL support, HTTP proxy support, customizable reports, and host authentication.