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Say I buy a prepaid sim-card with 3g data and put it in a used 3g modem (dongle) or a used smartphone and then create a Hotspot.

How would it technically be traced back to me? The ISP should see a Mac/IMEI of a device that isnt linked to me, and the IP is linked to an anonymous SIM-card.

Am I missing something here?

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They give away your location, and you have to buy them somewhere, which may have CCTV. Still, quite good anonymity –  paj28 May 15 at 21:57

2 Answers 2

many of the large mobile (internet) providers use huge NAT to manage internet access for their customers. I recently was doing a forensic job and was surprised to learn that some don't keep any track of their IP assignments to "handsets" against time/source port.

So if a web connected resource is trying to establish who was using an IP address associated with a 3G connected device (direct; no VPN etc) then some telecoms provider will not be able to satisfy their request simply because they don't store the information - at all.

This is interesting information for those that wish to have privacy online but what is not clear is exactly which mobile providers do this. Also, with the 3G provider that I dealt with (through a legal team) some of their devices/customers are monitored for IP address assignment and others aren't - e.g. the prepay USB 3G dongles are monitored, but prepay handsets aren't.

good for privacy - but a bit frustrating when you're an investigator!

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That's interesting. Thank you for the insight. –  Dave May 16 at 12:43

If you purchased any of these items with a creditcard or debitcard, and the serial numbers were recorded as part of the transaction, that chain of information could lead back to you. I am not certain how easy the backtracking would be; it depends on the retailers, their inventory and sales tracking, and the zealousness of the investigator. It is more likely -- given the scenario you describe -- that a system using this connection might leak information to the Internet that could be captured and cross-referenced with the ISP/wireless providers logs to identify the system owner/operator. Data leakage could include things of this sort:

  • Google account info (using Chrome browser, which is authenticated to the Google account)
  • Website or webapp credentials (logging in to a website, without a separate VPN/TOR/e2e encryption tunnel -- not just relying on server-side SSL/TLS)
  • Any one of a number of "phone home" utilities, protocols, or applications. (zombie/bot-net infection, calling to the CNC server; Windows Update; Red Hat Update Network)

A good starting point to learn what info may be used to identify someone is the EFF: https://panopticlick.eff.org/
https://tor.eff.org/about/overview.html.en#stayinganonymous

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Those issues would be easily solved by paying cash and using a live-CD linux distro of some sort, no? If I plug the SMS into a used Android phone, no phone home data will be linked to me anyway. –  Dave May 15 at 10:46
    
Indeed they would. I wasn't sure what your intent with the question was. It is possible to be mostly anonymous in your scenario, given you consider all the possible ways one could be identified. Nothing is perfect though, so I won't say "will be absolutely anonymous"... I was giving options on how one COULD be traced. If you mitigate all of them, you are less likely to be traced. –  0xSheepdog May 15 at 17:18

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