You've likely heard the warnings that public wifi can't always be trusted, and now Microsoft is giving you a good reason to avoid them. Users are accustomed to seeing these pop-ups when logging onto public networks, so they're less likely to be suspicious. How to keep your devices safe from public wifi attacksMicrosoft researchers are urging travelers to assume that public and guest wireless networks at hotels, conference centers, and airports are untrustworthy. Whenever possible, users should rely on private connections, such as mobile hotspots and cellular data, instead of logging onto public wifi. (You should never be required to download anything to connect to wifi.)