"If something is not meant to be on the internet, probably it shouldn't be there in the first place."
Information gathering is the way to gather all the relevant information from publicly available sources, and is often referred as Open Source Intelligence (OSINT). Passive reconnaissance through OSINT occurs during the first step of the kill chain when conducting a penetration test or an attack against a network or server target. An attacker will typically dedicate up to 75% of the overall work effort for a penetration test to reconnaissance, as it is this phase that allows the target to be defined, mapped, and explored for the vulnerabilities that will eventually lead to exploitation.
There are two types of reconnaissance: passive reconnaissance (direct and indirect) and active reconnaissance.
Generally, passive...