Netcraft

Netcraft is a UK-based internet services company known for its internet security and research services. One of its prominent offerings is the Netcraft Web Server Survey, which collects and publishes data about web servers, web technologies, and internet infrastructure.

Netcraft also provides services related to anti-phishing, anti-malware, and internet security, making it a valuable resource for organizations and individuals interested in monitoring and protecting their online presence.

In the context of passive infrastructure identification, Netcraft's services and tools can be used to gather information about internet infrastructure, websites, hosting providers, and the technologies used on the web.

Netcraft maintains a database of web server software and versions in use on the Internet. By querying it, you can identify the web server software (e.g. Apache, Nginx, Microsoft IIS) running on a website.

It can also identify the hosting provider or data centre where a website is hosted. Netcraft provides tools to analyze SSL certificates used by websites which can help identify CAs, certificate expiration dates and whether a website uses secure encryption protocols.