As stated earlier, the main goal of reconnaissance is to gather information while avoiding detection and alerts on intrusion-detection mechanisms. Passive reconnaissance is used to extract information related to the target from publicly available resources. In a web application penetration test, to begin you will be given a URL. You will then scope the entire website and try to connect the different pieces. Passive reconnaissance is also known as Open Source Intelligence (OSINT) gathering.
In a black box penetration test, where you have no previous information about the target and have to approach it like an uninformed attacker, reconnaissance plays a major role. The URL of a website is the only thing you have, to expand your knowledge about the target.
