Footprinting is the process of gathering public information about a computer system and its owning organization in order to learn as much as possible without accessing the system directly. The document provides an overview of open source footprinting techniques like whois lookups and examining a website's HTML, as well as port scanning and DNS interrogation. As an example, the author footprints the website 2600slc.org, discovering its IP address, admin contact details from the whois record, and open ports including FTP, SSH, SMTP, and HTTP. The information gathered through footprinting can be used to better attack or protect a system.