Stolen Bandwidth

I use a Networx monitor on my computer and usually use like 2-3 gigs a day, left my computer running while i went to sleep, When i woke up i looked at my Networx monitor and noticed it read a 300giabyte Download and upload amount since I went to sleep, this started like 30 mins after i left my computer idle and stopped when i started working on it, It shows me hourly usage and says that like 50-70 gigs an hour were being used, What happened? What caused this? and HOW DO I FIX IT?

via Bleeping Computer Last 20 Posts http://www.bleepingcomputer.com/forums/t/510590/stolen-bandwidth/