SIM

Subscriber Identity Module

In plain language

The small card in a phone that identifies your account with the mobile carrier.

The metaphor

Like the name tag your phone wears on the carrier's network.

Going deeper

How it works

It holds the phone number link and carrier details.
Scammers sometimes trick carriers into moving a number to their own card.
A PIN on the card helps.
Ask the carrier to add a port-out lock.

What can go wrong (example scenario)

A business owner's phone suddenly lost service. An attacker had persuaded the carrier to move the number, then used it to reset her email and bank passwords.

In practice

An owner adds a carrier PIN.
A firm uses an authenticator app so a stolen number gives no access.
A traveller buys a local card.

A question owners ask

What is SIM swapping?

When a criminal convinces the carrier to move your number to their own card, so they get your texts.

Related terms

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