Copyright infringement happens when a copyright owner notices you (or someone on your line) stealing a movie or music or other marked material media, and notifies your provider that they caught you. If YOU are not aware of the "theft", here are steps to follow
1) check ALL computers in your network.. Often a spouse, or teenage child will not be entirely truthful
2) verify your network security, If you have wireless enabled and your security is low, you can be held liable
3) contact the service provider, and they can tell you the approximate time and day the download happened, enabling you to better check.
4) reset your network security code, making sure it is not a simple passkey, and occasionally change it to ensure someone in the network isnt sharing it with others.
Remember, an open network, regardless if you are someone that feels the net should be free for all, makes you responsible for the things that happen through your network. If someone breaks copyright rules and downloads, you can lose your provider. Even worse, if your neighbor or the guy parked in the street download child porn, or engages in ilegal pedations (children), you can as easily be arrested and charged with the crime.
Lock up that signal folks, keep it safe.
This one tip will help you sleep better tonight
A few seconds are all you need to get a better night's rest.