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I want to make sure I understand the security implications of this scenario:

  • I am staying in a hotel.
  • I have a VPN on my android phone.
  • I connect to the hotel's unencrypted WiFi network with the phone.
  • I start a Wifi Hotspot on the phone. It has a secure password and WPA2 encryption.
  • I connect my laptop to the Wifi hotspot

I know that (barring a a proxy on the phone or a rooted phone with a modified routing table) Android doesn't route the laptop's connection through the VPN , but directly to the underlying network interface (the hotel's unencrypted Wifi).

My question is, what kinds of dangers does this setup expose the laptop to?

I believe that these statements are true: are they?

  • the phone would effectively be acting as a router, so the laptop would NOT have an IP address on the hotel WiFi network directly, but rather on the phone's own private network, with the phone being its gateway.

    • This means that potential attackers on the hotel WiFi network cannot send unsolicited packets to the laptop (i.e. can't port scan and such).
  • any unencrypted traffic received/sent by the laptop could of course be spied on by others on the hotel WiFi as it transited.

  • use of HTTPS would prevent anyone on the hotel wifi from spying on or injecting data into those streams (i.e. they couldn't modify an HTTPS website)

What other dangers are there for the laptop that I am missing?

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  • A WiFi hotspot shares the mobile broadband connection to other devices . If you use the WiFi hotspot feature on an Android phone, it disconnects any WiFi network it was connected to. Therefore, your scenario doesn't really exist, does it? Commented Nov 18, 2023 at 6:15
  • @EsaJokinen there are ways android.stackexchange.com/questions/201024/…
    – schroeder
    Commented Nov 18, 2023 at 9:16
  • The dangers depend on the Threat Model you are using. It's always possible that a few Mossad agents would kidnap you in the lobby and torture you into giving them all they want. It's possible an attractive young woman may be willing to sleep with you to get into your laptop while you are still asleep. It's possible your phone has a 1-day, be easily controlled remotely, and used to send packets to the laptop. I'll just use my phone's cellular data connection (or simply use an up-to-date kernel, eventually with a software FW on the laptop). Commented Nov 18, 2023 at 11:06
  • @esa-jokinen: A good thought, but it is not so. Just turned off mobile data on an unrooted Android 14 phone, turned on wi-fi hotspot and connected my laptop to that wi-fi hotspot, and was still able to get connection. Google help seems to specify that some phones are able to share wi-fi connection by tethering:support.google.com/android/answer/9059108?hl=en So the question is not moot (at least not always)
    – stochastic
    Commented Nov 18, 2023 at 19:21
  • It seems this has improved since I've last used Android. This question is interesting although the situation would be easily solved by using the VPN directly on the laptop. Commented Nov 19, 2023 at 4:01

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