KNemo is a Network monitoring program for Linux. The program stores information wrt the amount of data communicated thru your various LAN connections and also provides a way to automatically disable the internet on certain conditions.
KNemo is a simple addon program to your network management enabling you to control your internet usage. It also provides methods to disable internet in case you exceed the monthly bandwidth limit of your plan. Its an excellent tool to study your usage of internet over time.
To install Knemo on a ubuntu system, use the following command:
sudo apt-get install knemo