What threats does Android pose to anonymity when internet is accessed by a laptop through USB tethering but over Tor?

Question

I use USB tethering on an Android 10 mobile to access internet on my laptop. I use Tor browser (TB) on laptop and keep my OS (a Linux distro) on laptop patched for security vulnerabilities. At times I need to consume certain content from websites which I don't want any intermediary to know about.

Can my mobile device see what data I am requesting and receiving other than that I am connected to a Tor entry node and passing data to it back and forth?

Here's what I have in mind:

1. I enter security.stackexchange.com in TB's URL bar in laptop
2. TB establishes a secure connection and sends my request to Tor network.
3. My telecom provider, the first potentially hostile intermediary I usually think of can see only that I am connected to Tor network. For scope reduction of this question, let us become ignorant and assume that my ISP or any intermediary further down does not have the capability to either see my original request or link it back to me.

So far, reasonably good. But, the first intermediary seems to be the Android 10 device itself. How can I be sure that my Android 10 device cannot know what data I am requesting and receiving other than that I am connected to Tor?

I am concerned because my mobile device is potentially hostile in my eyes. I do not know the capabilities of the baseband OS (which some state sponsored entities may exploit), don't know the vulnerabilities of my Android 10 device which has vanilla Android fused with proprietary code. My mobile device is also at the mercy of its OEM which may not provide security updates for it in future.

Answer 1

As already mentioned in a comment, your phone is an intermediary to the same extent as our phone's ISP. They see exactly the same traffic. Therefore, any technology that protects you from a hostile ISP protects you equally from a potentially hostile phone.

This is under the assumption that the only thing that the phone can see is the network traffic from the laptop. There are actually two ways the phone could be a more powerful attacker. Neither are due to the fact that the laptop's network traffic transits via the phone, only to the fact that the phone is located nearby and connected to the laptop via a cable.

• If your laptop's USB stack is buggy, it might allow your phone to attack your laptop. The best remedy is to have an up-to-date operating system (and hoping your adversary doesn't have a zero-day on the OS drivers) and secure USB firmware (which you don't really have any control over, so don't obsess about it).
• A smartphone has a lot of sensors which can observe all kinds of side channels. For example, malware on the phone may be able to figure out what you're typing from the sound of the keys being hit.

This is movie-plot-level paranoia, well beyond FBI-level attackers, but possibly not beyond NSA-level attackers.

Tor protects you by routing all traffic through an encrypted channel so that any intermediary between your laptop and the Tor network (your phone, your ISP, connections between ISP, the Tor entry node's ISP, the Tor entry node) can see that you're using Tor and can see the volume and timing of data, but not the content nor the ultimate destination of the data. The usual limitations of Tor apply (traffic between the exit node and the ultimate server, a state-level actor that sometimes controls both the entry node and the exit node that you happen to use at that time and manages to correlate packets through timing, occasionally forgetting to use Tor, etc.). None of these limitations are made any worse by having a smartphone as the first network gateway out of your computer.

Answer 2

I would consider using a vpn for this. This way if Tor does leak some data your phone's internet connection would only be able to see that you are connected to a vpn.

If you only want a vpn for this reason you could easily host your own on a shared vps (like digitalocean) or at your own house for very cheap.

I don't know the intricacies of how the TOR browser works but I know the vpn would protect you in this case because your entire connection would be encrypted through the vpn.

Answer 3

Since you are using TOR , you will be actually safe. The data which is being passed through Android phone will be encrypted. Neither your phone nor your ISP will get to know what you are doing on your Laptop