Computer networks are constructed in such a way that it is possible to eavesdrop on the traffic on the local network that you are connected to. This implies that if you are part of a wireless network or share a switch/hub with others, then you can follow their traffic.
Exactly how much you will be able to see depend on the type of network you are connected to. In some networks, you can see all traffic while other networks only let you see so-called "broadcast" traffic. But even the broadcast traffic will give you an idea about what is going on at your network.
No matter what kind of network you are connected to there is, however, at least one computer that will let you see all traffic to and from it. That is your own computer.
With the program EtherApe you can watch who is communicating with whom on your local network, and not the least you can get insight into who your own computer is "talking to". Just start the program and wait a while. Then you should be able to observe the traffic. Every line in the EtherApe window represents a data connection. The thicker the line, the more data is exchanged.
We have two reasons for including EtherApe on this CD:
EtherApe is an excellent tool to keep an eye what your
computer is doing. Observe if it is contacting somebody that you did
not expect.
We want to demonstrate how easy it is to spy on a network. You will only see fragments of who are talking to whom. But your internet provider also has a local network: All the traffic of their customers goes through their network. If your provider is running a program like EtherApe, then he can see who all of his customers are talking to.
Recent European data retention laws even make it mandatory for the internet providers to observe traffic this way - and keep that information as log files. In Denmark, for example, the internet providers have log every data connection made by their customers and keep the log files for at least one year. Then the police can demand to get this information when they want it.
If you try out EtherApe on a network that has a bit of traffic you might be surprised to learn how much is revealed about everybody. However, there are several programs that can shows much, much more than EtherApe. They will show the contents of emails, homepages and much more. Even passwords can be extracted, unless you use a encrypted connection. We could have put one of those programs on this CD, but instead we opted for EtherApe, since it only reveals reasonably inoccent information ...
