Footprinting is the first and most advantageous way that hackers use to assemble data about PC frameworks and the organizations they belong to. The reason to learn as much as you can know about a framework, it's remote access capabilities, its ports and services, and the aspects of its security. It is essentially the initial step where hacker gathers as much data as possible to find ways to intrude into a target system or at least decide what kind of attacks will be more suitable for the target. It could be both passive and active. Reviewing a company’s website is an example of passive information gathering, whereas attempting to gain access to sensitive data through social engineering is an example of active information gathering.
Technique used for footprinting :