What SIM takeover fraud is#

Also known as SIM swapping. Criminals take control of your mobile number by transferring it to a SIM card they own, usually by:

  • Assembling enough detail to impersonate you, scraped from social media, leaked in an old breach, or coaxed out of you by phishing
  • Ringing your network and passing themselves off as the account holder
  • Reporting the handset lost, stolen or broken, so the number gets moved onto a SIM they hold
  • Asking for a PAC code, which lifts the number to a different network altogether

The moment that transfer completes, your number rings on their handset. Your bank, your email provider and every app that texts you a security code now reach the fraudster instead of you.

That gives them your calls, your texts, and your one-time passcodes for banking and social media. It's how they log in, reset passwords, and move money between accounts before you notice.

Criminals use these attacks to drain bank accounts, access cryptocurrency wallets, and take over email and social profiles.

Cifas Fraudscape data puts the increase in unauthorised UK SIM swaps at 1,055% during 2024, with close to 3,000 cases logged across the networks. Which? found reports almost doubled between 2022 and 2023, rising to more than 2,000 cases by late 2024.

Why it's becoming more frequent#

1. Your phone number is the gateway to your digital life. Many accounts rely on SMS security codes, making your phone the key to logging in.

2. Criminals need information, not technical skills. They just need enough personal detail to pass security checks with mobile providers.

3. The payoff has grown. As banks and identity checks have leaned harder on the mobile number as proof of who you are, capturing that number has become one of the shortest routes to somebody else's money.

How to know if it's happened#

It often happens suddenly and silently, but there are warning signs.

1. Sudden loss of signal. Your phone switches to "No Service" or stops receiving calls and texts. Fraud experts say this is one of the most common early indicators.

2. Network messages you weren't expecting. Confirmation that a new SIM is live, or notice of an account change you never requested. A great many victims describe exactly this — a routine-looking SIM notification, and then silence.

3. Locked out of online accounts. With your security codes intercepted, criminals can reset passwords and lock you out — sometimes within minutes.

4. Unauthorised transactions or login attempts. Alerts about banking activity or logins you don't recognise.

What to do next#

Act quickly.

1. Contact your mobile provider. Tell them you think your SIM has been taken over, and ask them to block the fraudulent SIM activation, secure your account, and reinstate your number on your original SIM. Providers know this type of fraud and can act fast.

2. Change your passwords, especially for online banking and email. Make sure each is unique.

3. Enable app-based authentication instead of SMS, so codes can't be intercepted.

4. Check your bank accounts for new payments, transfers or login alerts, and report anything unfamiliar immediately.

5. Report the incident to Action Fraud (opens external site), who track and investigate cases across the UK.

If your phone is lost or stolen#

A takeover isn't the only route to the same problem. If the handset itself goes missing, whoever has it may have your saved cards, your banking app and the number your security codes are sent to.

Work through these in order — the sequence matters, because the first two protect everything else.

1. Try Find My. Apple and Google both offer location services that can make the phone ring even on silent, and show its last known location. Worth doing before you assume the worst.

2. Lock it remotely. If it isn't nearby, securing it matters more than finding it. Both Find My services let you lock the phone so nobody can reach your data, and most let you display a message on the screen — a second number to call if someone finds it. Locking also stops anyone using the cards in your Apple or Google Pay wallet.

3. Change your key passwords. Email first, since that's the reset route into everything else. Then online banking, shopping accounts, social media, and any password manager.

4. Contact your mobile network. Ask them to block the SIM so nobody can make calls or receive codes on your number. They'll also advise on a replacement.

5. Report it if it was stolen. Tell your network and the police — 101, or your local station. If fraudulent transactions have already happened, report those to Action Fraud (opens external site) as well. They'll give you a crime reference number, which you'll likely need for an insurance claim and which lenders often ask for before removing fraudulent entries.

6. Watch your credit report. Fraudsters may use your details to apply for credit. The searches section of your report shows any hard searches made in your name — if one appears that you didn't authorise, contact that lender directly so they can investigate. What to do after identity fraud covers the steps from there.

How to protect yourself#

Keep personal information to a minimum online. Fraudsters use public information to impersonate you. Limiting what you share on social media makes passing your provider's security checks much harder.

Use strong, unique passwords. Reusing one password means that once criminals have it, they have all of them. Use longer, unique passwords with symbols and numbers.

Turn on account alerts. Many banks and email providers let you opt in to notifications for logins, password changes and suspicious activity — and to block login attempts from unfamiliar devices or locations.

The key things to remember#

  • Criminals move your number to their SIM, then receive your calls, texts and passcodes.
  • UK reports rose 1,055% in 2024, to nearly 3,000 cases.
  • Sudden "No Service" is the most common early warning sign.
  • An unexpected new-SIM confirmation message often arrives just before.
  • Contact your mobile provider first — they can reinstate your number.
  • Switch from SMS codes to app-based authentication.
  • Report it to Action Fraud.
  • Oversharing on social media is what lets fraudsters pass provider security checks.