On our company network, I have discovered that for the past 2-3 weeks, our Internet bandwidth has been maxed out to 100% consistently between the hours of midnight and 6 am. Our ISP has provided utilization graphs which verify that to be the case.
Our building is closed, and no one on site, during those hours, and no tasks are scheduled to run during that time that would make use of Internet bandwidth.
I am obviously concerned that either there is malware on a system or one of our servers has been hijacked or something along those lines, and I need to determine what is using that bandwidth. I would appreciate any thoughts on possible causes, and also thoughts on the best method of narrowing down where the utilization is coming from.