How does 'Wiretappers' pose a threat to the information system?

What is wiretappers?? 

Wiretappers is a large portion of the information processed by the company's computers travels over wires and cables. Some information is transmitted only from one room to the next, other information may be transmitted across the country via the Internet. These lines are vulnerable to wiretapping, which may be done with even inexpensive devices that are capable of performing the task without giving any clues that the wire is being tapped.

Wiretapping occurs all the time in for example crime movies. Spies and gangsters know the enemy is listening, so they speak in code over the phone and keep an eye out for bugs. In the real world, we may not think about wiretapping. Most of the time, we assume our phone lines are secure, and in most cases, they are, but only because nobody cares enough to listen in. If people did not want to eavesdrop, they could tap into almost any phone line quite easily.