Home Automation Systems are used more and more in new and modern buildings. They provide many comfortable functions, which make our daily life easier. Nearly every functionality in a building can be controlled with such a system, also security-relevant mechanisms like alarm systems. Therefore the security of the home automation itself should be as secure as possible. This fact should also apply to extensions like web interfaces for controlling smart homes via a web browser. This document examines different security aspects of the KNX technology as well as extensions, for example web interfaces which can also be part of an installation.