More and more HVAC/R components like fans, compressors or pumps are connected to the internet. Industrial Internet or Internet of Thing (IoT) are two names for a major technological trend today: a growing number of machines have connectivity features. Major expected advantages are energy saving, advanced maintenance and the reduction of machine downtime. Nevertheless, new threats occur: cyber security is a necessary condition for a long-term secure usage of those connected machines. Security against internet threats in an office IT-environment is typically based on secure connections (e.g. VPN,…), ongoing analysis of data (e.g. firewall,…) and algorithms to encrypt data. There are additional ways to detect internet attacks and even protect against them if industrial components like controllers or sensors are connected with the internet. These methods are not based on IT but on electro-technical principles. Due to this, they are less dependent on short term development cycles in IT and can fulfill the needs of cyber physical systems (internet connected sensors, controllers and machines), especially the need of security without frequent updates and patches. This paper presents four different approaches how to increase the security level of cyber physical systems and detect cyber-attacks or even protect against them.