Top Alternatives to skipfish

Nmap is a free and open-source utility for network discovery and security auditing. It utilizes raw IP packets to determine what hosts are available on the network, what services (application name and version) those hosts are offering, what operating systems (and OS versions) they are running, what type of packet filters/firewalls are in use, and dozens of other characteristics. It is command-line driven, though official GUI versions are also available.

Zenmap is the official graphical user interface (GUI) for the powerful Nmap security scanner. It provides an easy-to-use interface for performing complex network scans, making Nmap's capabilities more accessible to a wider range of users, from beginners to experienced security professionals.

Nikto is a powerful and widely-used open-source web server scanner designed to identify potential security vulnerabilities and misconfigurations. It performs comprehensive tests against web servers to detect dangerous files, outdated server versions, and version-specific problems.

Zed Attack Proxy (ZAP) is a free and open-source web application security scanner. It helps developers and penetration testers find security vulnerabilities in web applications during the development and testing phases.