Think turning off your phone protects you?

[spartadon]

Your device carries two unique codes that follow you everywhere. You can’t change them. You can’t hide them. IMEI and IMSI.
Every time your phone connects to a mobile network, it leaves a trace. No apps needed. No browsing. Just sitting in your pocket.
These IDs reveal:
- What phone you use
- Which tower you connect to
- Where you are
- Which line is yours
- When you swap SIMs
- Even who was nearby

This thread explains what IMEI and IMSI are, why they’re dangerous for your privacy, how they track you, and how to reduce that risk.
Let’s go

What’s IMEI?
The International Mobile Equipment Identity.
A unique number hardcoded into your device, like a license plate.
You can’t change it easily.
Used to:
- Identify your phone
- Block stolen devices
- Link your movements to the same device, even with a new SIM

What’s IMSI?
The International Mobile Subscriber Identity.
Stored on your SIM card, it ties your line to your network.
It reveals:
- What SIM you’re using
- Who your provider is
- If you changed SIMs - If it’s still the same person (based on phone or behavior)
IMEI + IMSI = complete surveillance.


How does it track you?
Each time your phone connects to a tower, it sends your IMEI and IMSI in cleartext.
Towers log:
- Time
- Location
- Your device and SIM ID
- Often, the IDs of phones nearby too
This builds a detailed map of your movements and associations.
Who has access to this data?
- Your carrier
- Intelligence agencies
- Cell tower operators
- Forensics teams
- Sometimes, criminals using rogue devices (Stingrays)
This tracking doesn’t require consent or alerts. It’s invisible. Constant. Pervasive.

How to reduce mobile tracking?
You can’t eliminate it entirely, but you can lower exposure:
- Use phones that randomize IMEI (rare)
- Change both SIM and phone regularly
- Use GrapheneOS or de-Googled phones
- Use airplane mode often
- Prefer WiFi + VPN + Tor (when possible)
- In extreme cases: use anonymous burner phones
- Don’t register your SIM with real ID if possible
- Don’t fall for the “I’ve got nothing to hide” trap
Example
You change your number and SIM. Still use the same phone? Tracked via IMEI.
You change phones. Keep the SIM? Tracked via IMSI.
You change both, but keep the same habits, location, and timing?
Your pattern gives you away.

TL;DR:

IMEI = your phone
IMSI = your SIM
They track you even if you don’t open a single app.
Mobile privacy starts before your apps.
It starts with your hardware and the network.
Do what you can, but take the first step.

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[spartadon]

Side Quest: Card yourself a Google Pixel phone