Microsoft Wi-Fi Sense is a feature that allows a Windows 10 mobile end user to automatically connection to the Internet from a wireless Hot Spot that another Windows 10 user has previously connected to and shared. Wi-Fi Sense eliminates the need for Windows 10 users to manually discover and log into Wi-Fi networks for Internet access as long as the user is within range of a shared network.
To facilitate easy Internet access, Microsoft maintains a database of public (open) Wi-Fi networks that Windows 10 users have crowdsourced and shared. Wi-Fi Sense also allows individuals to share Internet connectivity from a private wireless network without revealing the network's credentials. Microsoft promotes this capability as a security feature because wireless LAN (WLAN) credentials are encrypted and stored on secure Azure servers instead of on individual mobile devices. Wi-Fi Sense is enabled by default during the Windows 10 Express installation and can be disabled or re-enabled through a device's Wi-Fi settings menu.
To ensure that access to a Wi-Fi network can never be shared with Wi-Fi Sense, a network administrator must modify the service set identifier (SSID) by adding the string "_optout." For example, if the network is called "XYZwifi," the SSID should be changed to "XYZwifi_optout." Enterprise Wi-Fi networks that depend on the 802.1X protocol for user authentication cannot be shared with Wi-Fi Sense because the protocol uses a central authority to authenticate credentials.
There are several security concerns about Wi-Fi Sense, one of which is called the "friend of a friend" problem. If Alice used Windows 10 and logged in as a Wi-Fi guest while waiting for a dentist appointment, for example, she would be asked whether she wanted to share her guest connection with her Facebook friends and Outlook/Skype connections. She could not choose which individual connections she wanted to share with in each application, she would have to select all or none. Consequently, if Alice checked "share this connection with Facebook friends" and Bob (Alice's Facebook friend) had an appointment with the same dentist later that week, Bob's mobile device would automatically have a connection to the Internet when it came within range of the dentist office's wireless network. Bob could not, however, access the dentist's network itself or extend his Internet connectivity to Eve, even if Eve used Windows 10. For those concerned about "the friend of a friend" problem, Microsoft recommends that private network hosts change guest passwords frequently.
Wi-Fi Sense was first introduced as a feature of Windows Phone 8.1 in order to provide mobile phone customers with more connectivity options.