What are the techniques utilized for foot printing?

Footprinting is nothing but accumulating and revealing as much as data about the target network before gaining access to any network.
Open Source Footprinting: It will search for the contact data of administrators that will be utilized for guessing password in Social Engineering
Network Enumeration: The hacker attempts to distinguish the domain names and the network blocks of the target network
Scanning: After the network is known, the second step is to spy the active IP addresses on the network. For distinguishing active IP addresses (ICMP) Internet Control Message Protocol is a functioning IP address
Stack Fingerprinting: the final stage of the foot printing step can be performed, once the hosts and port have been mapped by examining the network, this is called Stack fingerprinting.