Mobile Networking · Network Privacy · Lesson 5 of 5

Challenge: Hotel Privacy Check

Help a friend pick the right privacy tools on hotel Wi-Fi.

The Case Brief

Your friend Lee is staying at a hotel for a work trip and has to use the hotel Wi-Fi. Lee reads the hotel's terms and finds a line saying the network keeps logs of guest traffic. Lee asks you to help set up some privacy protection on an Android phone.

Lee's main worry is the hotel learning which websites and services the phone uses. Lee already knows HTTPS keeps page contents private, but has heard that site names still leak.

You start with the simplest step. You open the Private DNS setting and choose Private DNS provider hostname, then enter dns.example, a resolver Lee trusts. Lookups now travel encrypted with DNS over TLS.

Lee asks whether that's the end of it. Can the hotel still learn anything about where the phone connects?

The Hotel Pushes Back

The next morning, Lee messages you. The phone says the hotel Wi-Fi has no internet access, even though Lee's laptop on the same network loads pages fine.

You check the hotel's network page. Under a section about security, it says the hotel blocks port 853 for all guests. Everything else on the page looks normal.

Lee hasn't touched the phone's settings since last night. Private DNS is still in hostname mode, pointed at dns.example.

Trying a VPN

Lee switches Private DNS back to Automatic and turns on a paid VPN app instead. With the VPN on, Lee does three things:

• browses a few news sites
• signs in to a work email account
• checks a free weather app that includes an ad network's SDK and reads the phone's advertising ID

Lee asks which of these the VPN actually protects, and from whom.

A Friend's iPhone

Lee's coworker Ana is at the same hotel. She pays for iCloud+, and Private Relay is switched on for her iPhone.

Ana prefers a different browser app, not Apple's. She visits a site that shows your IP address and is surprised to see her normal address there, not a temporary one. Private Relay is working for some things on her phone, just not this one.

Ana wants the browsing to go through Private Relay without paying for anything extra.