ay the intruder can get hold of, for example, bank account numbers and passwords. Other attacks can hit the routers, whether seen as control or connectivity elements. The routing plan uses routing tables in the routers for controlling traffic flows and making decisions based on packet content and configuration. The routers are accessible through the network and are therefore often targeted by attackers trying to hack their way in. If an attacker can control the traffic flow in the network, he can get his own packets to any destination (misrouting). The charging system is of course interesting for hackers, as well. The signalling systems are the nerve systems of the communication. Protection of signalling (SIP, SDP) traffic has priority. Regarding the connectivity layer, transmission is a weak part for eavesdropping in radio systems. At low level, hardware such as switches and relays might be destroyed. Electronic attacks can make the network stop working. Wires could be cut. Fire and water are other risks. Attacks on the management part may be more severe than others. Management security is of particular concern regarding both network protection against intentional damage Understanding Changing Telecommunications - Building a Successful Telecom Business (sabotage from hackers and intruders) and fraud detection and prevention. A very strict authorization and authentication is therefore necessary. At the service and content layer the network can be flooded, leading to denial of service. Virus attacks and other malicious programs hit the contents. Data get corrupted. Unauthorized users gain access to the communication network. False data is inserted. Money can be transferred to the wrong receiver. B2B and B2C transactions are disturbed. What can we do with the network, to protect it? Let us use a metaphor and consider the network as a house, that we want to protect. We can close the doors and windows and lock them. Then we can give a key only to those we want to access to our house. This is an organizational way of 