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Comment by derefr | Hacker News Reader

Yesterday I was pondering what the ultimate “side-piece” phone would be (that is, a secondary phone you use for OPSEC when leading a second life.)

Unlike a burner phone, you wouldn’t constantly be throwing it away (just getting new SIMs every once in a while) so cheapness would not be the #1 priority—but it would still be #2 or #3, since this is still a whole 'nother phone you have in addition to the phone you usually use. And you’d want it to be ergonomic to text on, so a 1990s candybar dumbphone wouldn’t quite cut it. It wouldn’t need apps like a modern smartphone (other than maybe messaging apps.) And battery life would be important—it's often hard to find private time to charge a secret phone—so a big screen would be a drawback, not a positive.

Ultimately, I figured that an old Blackberry would be perfect for this use-case. Guess I deduced correctly.

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Both the SIM and the phone's serial number are available to the network. An analyst looking to correlate your activities can do so trivially. In fact, this is how Italian investigators were able to prove the link between a CIA cell and the American embassy. No one used the same SIM to talk to both groups, but they did use the same phone.

https://www.youtube.com/watch?v=BwGsr3SzCZc

IMEI is unfortunately a mutable value on many devices.

An extreme example which is used for SMS/Voice spam: https://www.aliexpress.com/store/product/GPRS-sms-64-sims-mu...

I might be wrong but I always thought this requires some pretty high level of operational discipline, because its detectable and highly suspicious when you switch the IMEI while the phone is switched on and the same card is in the phone. You have to turn off the phone, remove the sim, turn on the phone and switch the IMEI, turn it off again and put another SIM in, and then turn it on again. Otherwise the Telecom provider will register the anomaly and might even inform the authorities or kick off the phone from the network.

Again, please correct me if I'm wrong.

A proper side phone could be programmed to handle this process correctly. In an option accessible from a menu it could drop the network, prompt to switch out a SIM (or use one in a different slot), wait a suitable amount of time, and then reconnect to the network.

I see no reason to reboot the phone. SIMs can be hot-swapped.

You can configure (rooted) Android to not connect to mobile network until you tell it to do so

Yes, sure, the IMEI is accessible; this is why I referred to it as a "side-piece phone" rather than a "burner phone." They're separate OPSEC profiles: evading a state attacker, vs. anonymizing some of your traffic from the view of a private individual attacker (e.g. your spouse.)

Step 0 is to correctly identify the threat model. If you're just hiding an affair from your spouse, any old smartphone on a prepaid contract will do.

> Unlike a burner phone, you wouldn’t constantly be throwing it away (just getting new SIMs every once in a while)

In that case, you probably also want to rotate IMEIs, right? I don't know if the feds are routinely considering it, but they could correlate all the SIMs by looking at the unchanging IMEI.

A side-piece phone isn't a burner phone (thus why I said "unlike a burner phone.") A burner phone is a phone used to avoid unification of identities by the state; a side-piece phone is a phone used to avoid unification of identities by private individuals. The usual example being your wife trying to figure out if you're cheating on her, but here's a few other examples:

• your wife's lawyer in divorce-court, who would love to compel cell-tower IMEI logs, but has no legal grounds to do so

• your mother who you don't want to be made aware that you're a working as a prostitute

• your abusive partner or parent who you're trying to arrange an exit from

• or, the ever-present cloying example: your friend—who is very nosy and knows your regular phone's unlock code—but who you're trying to arrange a surprise party for

Basically, as a burner phone is to Tor, a side-piece phone is to a browser's Incognito Mode.

Why wouldn't your 'side-piece phone' just be another normal phone? What does removing the camera and GPS module have to do with any of those scenarios?

derefr didn't suggest to remove the camera or GPS. derefr just wanted a phone that's easy to text on, not too expensive, and has a long battery life.

Lowers the cost? While not paramount in a non-burner scenario, lower cost is generally preferable.

It's also not very difficult to change your IMEI..This would make it quite complex for feds to investigate, I presume.

Not necessarily, see my other comment. If the Telecom company cooperates, they could even look for phones in the network that switch the IMEI and scrutinize these phones particularly, because there is almost certainly something dubious about them.

Unless people turn off the phone and remove the SIM before switching it should generate highly suspicious network traffic.

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