Footprinting (also known as reconnaissance) is the technique used for gathering information about computer systems and the entities they belong to. To get this information, a hacker might use various tools and technologies. This information is very useful to a hacker who is trying to crack a whole system.
When used in the computer security lexicon, “Footprinting” generally refers to one of the pre-attack phases; tasks performed before doing the actual attack. Some of the tools used for Footprinting are Sam Spade, nslookup, traceroute, Nmap and neotrace.
Footprinting helps to:
Know Security Posture – The data gathered will help us to get an overview of the security posture of the company such as details about the presence of a firewall, security configurations of applications etc.
Reduce Attack Area – Can identify a specific range of systems and concentrate on particular targets only. This will greatly reduce the number of systems we are focussing on.
Identify vulnerabilities – we can build an information database containing the vulnerabilities, threats, loopholes available in the system of the target organization.
Draw Network map – helps to draw a network map of the networks in the target organization covering topology, trusted routers, presence of server and other information.
Source:
https://en.wikipedia.org/wiki/Footprinting
https://www.greycampus.com/opencampus/ethical-hacking/what-is-footprinting