This is not a direct solution to your problem, but might help you to find out what is happening.
You could use a tool to analyze the traffic on your computer in order to see what is going on.
Sysinternals is a good place to start for different windows tools.
Sysinternals Networking Utilities[
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Look for TCPView. It will show you which connections you have open, but doesn't contain a monitor.
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TCPView is a Windows program that will show you detailed listings of all TCP and UDP endpoints on your system, including the local and remote addresses and state of TCP connections.
For a network monitor you can try this tool from Microsoft
Microsoft Network Monitor 3.4[
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Tool to allow capturing and protocol analysis of network traffic.
If it is an application you have the source code for, you can always add a logging functionality that writes sent and received data to a file.
If you create a new file every 5 or 10 minutes, you can see how much data that is transferred within this time frame.