Ethical Hacking
Network security consists of the policies and practices adopted to prevent and monitor unauthorized access, misuse, modification, or denial of a computer network and network-accessible resources. Network security involves the authorization of access data in a network, which is controlled by the network administrator.
Because networks ensure connections between different types of terminals, various and numerous data flows through them. Some part of that data is wished to be kept private because it can contain personal informations, GPS locations or even credentials to access different bank accounts. This means that kind of data is valuable and some try "stealing" it. This kind of "stealing" information from a network is generically called "Hacking" and it is illegal.