Reconnaissance is 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 seventy-five percent 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, and active reconnaissance.
Generally, passive reconnaissance is concerned with analyzing information that is openly available, usually from the target itself or public sources online. On accessing this information, the tester or attacker does not interact with the target in an unusual manner—requests and activities will not be logged, or will not be traced directly to the tester. Therefore, passive reconnaissance is conducted first to minimize...