According to Ars Technica, Windows 10 will still send telemetry and other data to Microsoft-owned domains — no matter how tightly you crank down the privacy settings. Even with everything buttoned down, Cortana, OneDrive, and Web Search from the Start Menu disabled, the OS still phones home, using a random system ID that persists across reboots. It apparently also tries to bypass proxies to do it. "Some of the traffic looks harmless but feels like it shouldn't be happening. For example, even with no Live tiles pinned to Start (and hence no obvious need to poll for new tile data), Windows 10 seems to download new tile info from MSN's network from time to time, using unencrypted HTTP to do so. ... Other traffic looks a little more troublesome. Windows 10 will periodically send data to a Microsoft server named ssw.live.com. ... The exact nature of the information being sent isn't clear—it appears to be referencing telemetry settings—and again, it's not clear why any data is being sent at all. We disabled telemetry on our test machine using group policies."