In VS2015 there was various stuff running in the background, like \"VsHub\", etc. It connected to MS servers, and possibly leaked stuff. So the common approach was to delete tho
I turned off CodeLens and it instantly went down to 0%.
In VS: Tools->Options: TextEditor->AllLanguages->CodeLens
Uncheck Enable CodeLens
If you don't want to completely disable it you can try turning various things. TFS related things like Incoming changes would explain the Network activity as highlighted earlier.