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The vast majority of modern day mobile devices have a fixed IMEI number that's impossible to change, which makes it easy to track people if they use the same device constantly. It's quite easy to swap SIM cards frequently if you wish to stay anonymous, however throwing out whole devices can quickly get too expensive.

What's the reason behind this? Why not let users randomize their IMEI number if they wish?

  • 3
    The entire point of IMEI is to identify device. If you can change the real IMEI, that'd be missing the point, especially when IMEI is usually the number used to track stolen devices. It's like you can't really change your car's VIN, or fingerprint, or birth certificates. It's actually possible to change the IMEI your device claims to be that's visible to most software, there are some IMEI changer app that does this, but they won't really change the IMEI that's been etched inside the phone. – Lie Ryan May 24 '18 at 11:09
  • @LieRyan however this means that someone who wishes to stay 100% anonymous has to throw out his mobile device every week to be safe. – JonathanReez Supports Monica May 24 '18 at 11:20
  • @JonathanReez or they could just not use apps that can access it? The carrier is still going to know who you are. – multithr3at3d May 24 '18 at 13:25
  • @multithr3at3d in most Western countries the carrier has no idea who I am. – JonathanReez Supports Monica May 24 '18 at 13:50
  • @JonathanReez So how do you pay them? – multithr3at3d May 24 '18 at 13:51
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The IMEI is a global fix identifier for a phone. In some countries, if your phone is stolen and if you have noted its IMEI, you can communicate it to a central organization that ask all local operators to blacklist it, making the phone unusable on the entire country.

Allowing a user to simply change it would immediately break that feature.

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Quite simply, because the standards for mobile networks require that the IMEI is unique. To allow users to change it would violate the standards.

The International Mobile Equipment Identity number (IMEI) uniquely identifies an individual mobile station. The IMEI is unique to every ME and thereby provides a means for controlling access to GSM networks based on ME Types or individual units.

The assigning of the IMEI is strictly controlled:

The term Reporting Body shall refer to a Body that is recognised by the GSM Association as having authority or competence to allocate IMEIs to ME Types. These Bodies may have also been given authority by their national governments or industry bodies to perform a regulatory conformity assessment procedure or otherwise permit the use of mobiles on networks. There may be more than one Reporting Body in a country.

(source: https://www.gsma.com/newsroom/wp-content/uploads/2012/06/ts0660tacallocationprocessapproved.pdf)

In addition, some jurisdictions require that the IMEI be used to block access to mobile networks, and make the changing of the IMEI illegal:

Re-programming mobile telephone etc.

(1)A person commits an offence if—

(a)he changes a unique device identifier, F1...

(b)he interferes with the operation of a unique device identifier.

[F2(c)he offers or agrees to change, or interfere with the operation of, a unique device identifier, or]

[F2(d)he offers or agrees to arrange for another person to change, or interfere with the operation of, a unique device identifier.]

(source: http://www.legislation.gov.uk/ukpga/2002/31/section/1)

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The IMEI serves as a globally unique identifier, like a MAC address in IP-based systems. Think of the

  • IMEI as the MAC address
  • IMSI (SIM Card number) as the IP address

To arbitrarily connect to a globally routeable system, a device MUST be uniquely identifiable. Otherwise, collisions will occur.

Addendum as per the comments:

You CAN change the IMEI number with a hack, but you should not do that of course. Likewise you may also forge a SIM card, this will allow you to impersonate a user (and generate cost to them). I believe either of these would be a criminal act in most jurisdictions.

Additionally, creating duplicate identities may put these on a black list.

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    What happens if two devices has the same IMEI number? What if they also 'happen' to have the same Sim card number? – Jacco May 24 '18 at 11:00
  • But you CAN change the MAC. You may break your network, but somebody with a "homebrew phone" could break a cell network as well by faking an IMEI. So the option to change it could be there like it is for a MAC. No default option, but some hidden setting. – allo May 24 '18 at 12:01
  • @Jacco the phone will probably be blocked forum.xda-developers.com/showthread.php?t=365347 quora.com/… – Rsf May 24 '18 at 15:00

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