Network security is about protecting and controlling the communication between systems and devices. Network security is essential for conducting transactions and communications among businesses, government agencies and individuals. The concept of security protocol means a specification for exactly how data shall be transmitted in a secure way between systems, and typically involves encryption and digital signatures. The most prominent communication platform is of course the Internet, for which there are many different security protocols. Other network technologies are e.g. Bluetooth, mobile, industrial networks, in-car networks, and satellite links, for which there are also various security protocols. Two different aspects of network security are the security of the data transmission itself, which is called communication security, and the security to protect computer networks of organizations from attacks, which is called computer network security.