Annonymity through prepaid mobile plans

Question

In my country you can buy a prepaid plan without ID. Lets say I buy two 4G dongles, connect both of them to a Rasperry Pi, pipe my connection trough the first dongle to the second dongle, hide the Pi in a public building ceiling and power it from the AC-line.

Assume that nobody find the Pi, the data is encrypted, no DNS or WebRTC leakage and I'm not using any of my personal accounts (eg. bank). Is there anyway that the ISP or someone else can find out where the data originally came from (IP address etc)?

Answer 1

Summary: Don't do it.

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Your question is mainly about anonymity. So I'll address that first:

• You are talking about buying three pieces of hardware and two SIM cards. Each of these have an identification, which could possibly be tracked back to time and location of sale. At that point it could possibly be tied back to a CCTV recording or a card used to pay for the purchase.
• There is also the possibility of a CCTV catching you in the act of hiding the device.
• Finally you would want to communicate with this device. Both the ISP that you use to get in touch with this device as well as the ISP you use to establish connection to the device will likely have records indicating which pair of IP addresses are communicating.
• There are plenty of ways in which the association between the two 4G dongles could be established. First of all you might have bought both at the same time, secondly the provider will know the approximate location of both dongles which happen to be the same and hardly ever changing.

As for the legality there are multiple reasons why what you are asking about might be illegal:

• You might be violating trespassing laws when installing the device.
• Even if you are allowed to be in that location, you might not be allowed to leave any of your personal belongings behind, when you leave that location again.
• Hooking into an AC line without permission is almost certainly illegal and could potentially get you electrocuted.
• You may be liable for the disruption caused by evacuation of the building and the bomb squad sent in to remove the device if the first person to find it does not have a clue what it is.

The reliability of such a device is unlikely to be good:

• There is the possibility of the network access provided by your SIM cards to go through a CGN which means connecting to this device remotely can be difficult or even impossible.
• If you were able to hide it in a public place there is the possibility that somebody else could find your device and modify and/or steal it.
• If you ever return to the device in order to service it, there is no way of knowing who might be waiting there for you. (But they will probably suspect you to be a terrorist.)
• The connectivity of either 4G dongle or the power supply could change in unanticipated ways with no warning.

Answer 2

I would need more details on your threat model to determine who would be looking, how competent they are, and how motivated they would be.

That being said, unless you are planning some light treason at a 3 letter agency, or your facility is otherwise obscenely security focused, there is a vanishingly small chance

1. they would ever even find the hardware
2. they would be motivated and/or willing to trace said hardware
3. that hardware purchased carefully with cash, intermediaries, and/or pseudonymously would lead back to you via that route.

So, the technical aspect of something like this is not going to get you. You need to worry about:

1. if discovered, will people assume it was the only nerd in the office who also happened to have a plausible motivation (investigations don't start with forensic analysis, they start by identifying means/motive/opportunity and work backwards)
2. complacency: after 6 months of no one noticing, you will get lazy, sloppy, start accessing it from the same locations multiple times, then probably just doing it from home, at which point, the sheer number of tor network activity correlations would be enough to damningly implicate you, even if they can't prove it with 100% technical certainty.

When someone get's killed, they just go interview that persons spouse. When they find a spy device in the ceiling of your work, they're probably going to interview you.

Non-technical operational security considerations are almost always vastly under-attended to and usually the thing that bones people.

Answer 3

It seems to me that you are constructing a very small, private, unoptimized, and untested TOR network. Therefore, we can expand your question to: "Can I be deanonymized while using TOR?"

The answer to that is yes, using various techniques that are available to varying levels of sophisticated attackers, which have been detailed in the security news.

Since your system is less robust than TOR, we can assume that it will be correspondingly easier to find you. Your system is particularly vulnerable to prediction, because you just have 1 entry node and 1 exit node.

You seem to think that physically hiding the system will make it more secure, but (as kasperd points out), it only exposes you to unnecessary risk. The speed bump of "unknown server in an unknown location" isn't harder technically if the server is hidden, as opposed to in Bermuda.