Some new Windows 10 users have been caught off guard by a new peer-to-peer (P2P service in the new OS that relies on a customer's upload bandwidth to distribute updates and apps.\nThe technology, which Microsoft calls "Windows Update Delivery Optimization" (WUDO), is turned on by default for all editions of Windows 10. But only some versions -- notably Windows 10 Home and Windows 10 Pro -- are set up to deliver updates and apps to other devices when connected to the Internet.\nThe versions used mainly in the enterprise -- Windows 10 Enterprise and Windows 10 Education -- only share updates and apps within a local network.\nHere's the low-down on the update techniology:\n\nWUDO in many respects resembles BitTorrent for file-sharing, using P2P to spread the load to PCs worldwide rather than relying on centralized servers.\u00a0Note: WUDO doesn't replace Microsoft's standard delivery service, Windows Update; it's an add-on technology.\nWith WUDO enabled, Microsoft can point others to locally-cached copies of updates and apps on users' Windows 10 devices connected to the Internet. In effect, a Windows 10 PC acts as a substitute server for others; any customer whose device is tapped for WUDO delivery has already given Microsoft access to their upload bandwidth.\nThough many users hadn't heard of it before now, WUDO was no secret: The company first touted P2P update deliveries in May as a new feature for Windows Update for Business (WUB), which is aimed at organizations running Windows 10 Pro, Windows 10 Enterprise and Windows 10 Education. (The service was also enabled by default in Windows Insider builds before last week's public launch of Windows 10.)\n\nSome users were annoyed: "P2P [peer-to-peer] isn't bad. But it should not be turned on by default!" wrote someone identified as RMJ1984 on Reddit. "It's totally unacceptable just using peoples' bandwidth."\nMicrosoft has not yet made public any technical documentation about WUDO, but the service can be turned off or restricted. To do so, go to "Settings," click the "Update & security" icon, then the "Advanced options" link under "Windows Update." In the next window, select "Choose how updates are delivered" and turn off WUDO by moving the slider to Off. To simply restrict sending locally cached updates and apps to devices on the same local network, choose "PCs on my local network" near the bottom.\nWith reports by Gregg Keizer at Computerworld.