Back in the days of dialup Internet access, this service was used by Internet Service Provides to control and bill their user's access.
Clobberd is a daemon that runs on a Terminal Server (ie: A computer will lots of modems connected to it), and monitors the activity of users connected to the terminal servers modems.
For user monitoring, clobberd monitors the utmp file (typically /var/run/utmp), monitors a given user's time spent online, what network interfaces they are using (ie PPP), and how much network traffic they are creating. It monitors all this information, and regulates them according to a set of restrictions.
For network interface monitoring, it will simply monitor the amount of traffic, and the time it is active. No regulation is done.
Users are able to view their stats via a web page, and a remote maintenance facility allows you to maintain user data from anywhere on your network.
Clobberd is written in C with an ncurses GUI.
Nb/ Dialup internet has been obsolete for years now, and so is this software. Back in the day, this software was highly sought after by ISPs.