Some important security parts of Linux were developed by the (Inter)National Spying A**holes.
As long as you are not able to encrypt your traffic end-to-end they can see everything. And this full encryption is impossible with a WAN connection.
You can secure your E-Mails with S/MIME or PGP/GPG,
You can encrypt your internet traffic with openVPN to connect to your own server(s) or PCs of your family or friends.
But as soon as you want to visit a website you need to break out of your VPN and you are visible again.
Thinking about the Tor Network? Forget it: hijacked by NSA, GCHQ, FSB, BND..
The only way to keep your private data really private is:
Going offline...