Perhaps it's better for you to delete all antivirus programs, all firewalls and finally the operating system - it definitely sends data.
There are traffic monitors that can analyze, WireShark for example, but for you it needs to be analyzed too. Monitor to monitor - that's crazy.
It's not random, you have to check... But is so hard to check, it's easier just to say something...
To put your mind to work, I'll give you just one keyword: BPB