Before attacking a network, attackers try to find out some important information like IP address of machines on the network, the operating systems that machines are using connected to a network, and the services that they offer. Using this information, attackers can be more focused on their attacks and it is less likely to cause alarm. The process of gathering all the information is known as mapping.
Strong encryption services that are based on cryptography only are its counter measures. Otherwise, it gets easy for attackers and others to read your data as it traverses the network.