Footprinting is the technique to collect as much information as possible about the targeted network/victim/system. It helps hackers in various ways to intrude on an organization's system. Footprinting can be active as well as passive. Passive footprinting/pseudonymous footprinting involves collecting data without the owner knowing that hackers gather their data. In contrast, active footprints are created when personal data gets released consciously and intentionally or by the owner's direct contact.
Some branches of footprinting :
Open-Source Footprinting :
This type of footprinting is the safest, holding all legal limitations, and hackers can do it without fear because it is legal and, hence, coined the term Open-source. Examples of this type include: finding someone's email address and phone numbers, scanning IP through automated tools, searching for age, DOB, house address, etc. Most companies provide information about themselves on their official website without knowing that hackers can take advantage of it.
Network-based Footprinting :
Using this footprinting category, hacktivists can retrieve information such as user name, information within a group, shared data among individuals, network services, etc.
DNS Interrogation :
After gathering the information from the different areas using various techniques, the hacker usually queries the DNS using pre-existing tools. Many freeware tools are available online to perform DNS interrogation
