Footprinting refers accumulating and uncovering as much as information about the target network before gaining access into any network. The approach adopted by hackers before hacking
Open Source Footprinting : It will look for the contact information of administrators that will be used in guessing the password in Social engineering
Network Enumeration : The hacker tries to identify the domain names and the network blocks of the target network
Scanning : Once the network is known, the second step is to spy the active IP addresses on the network. For identifying active IP addresses (ICMP) Internet Control Message Protocol is an active IP addresses
Stack Fingerprinting : Once the hosts and port have been mapped by scanning the network, the final footprinting step can be performed. This is called Stack fingerprinting.