Footprinting is an ethical hacking technique used to gather as much data as possible about a specific targeted computer system, an infrastructure and networks to identify opportunities to penetrate them. It is one of the best methods of finding vulnerabilities.

The process of cybersecurity footprinting involves profiling organizations and collecting data about the network, host, employees and third-party partners. This information includes the OS used by the organization, firewalls, network maps, IP addresses, domain name system information, security configurations of the target machine, URLs, virtual private networks, staff IDs, email addresses and phone numbers.

There are two types of footprinting in ethical hacking:

active footprinting

passive footprinting

What is active footprinting?

Active footprinting describes the process of using tools and techniques, like using the traceroute commands or a ping sweep -- Internet Control Message Protocol sweep -- to collect data about a specific target. This often triggers the target's intrusion detection system (IDS). It takes a certain level of stealth and creativity to evade detection successfully.

What is passive footprinting?

As the name implies, passive footprinting involves collecting data about a specific target using innocuous methods, like performing a Google search, looking through "Archive", using NeoTrace, browsing through employees' social media profiles, looking at job sites and using Whois, a website that provides the domain names and associated networks fora specific organization. It is a stealthier approach to footprinting because it does not trigger the target's IDS.