What is SIM takeover fraud and how can you prevent it?

If you’ve ever suddenly lost mobile signal for no obvious reason, you might have shrugged it off as a network glitch or a patch of poor reception. Most of the time, that’s exactly what it is. But it’s worth keeping in mind that it could be a sign of SIM takeover – sometimes known as SIM swapping or SIM-swap fraud.

What is SIM takeover fraud?

SIM takeover fraud is when criminals take control of your mobile phone number by transferring it to a SIM card they own. Usually, this is done by:

• Collecting your personal information (often from social media, previous data breaches, or phishing messages).

• Contacting your mobile provider while pretending to be you.

• Convincing them to activate your number on a new SIM card by claiming your phone was lost, stolen, or damaged.

• Requesting a PAC code to move your number to a different network entirely.

Once your number is moved over, the fraudster’s phone becomes your phone – at least in the eyes of your bank, your email provider, and any app that sends security codes via text message.

What makes SIM takeover fraud so dangerous? It gives criminals access to your calls, your texts, and your one‑time passcodes for logging in to accounts like banking and social media. In many cases, this is how they log in, reset passwords, and move money between accounts without you noticing until it’s too late.

Criminals often use these attacks to drain bank accounts, access cryptocurrency wallets, and take over email and social media profiles. Reports of unauthorised SIM swaps in the UK surged by 1,055% in 2024, with nearly 3,000 cases recorded across telecom providers, according to Cifas’ Fraudscape data. Consumer groups have also reported a sharp increase: Which? found that SIM swap fraud reports almost doubled between 2022 and 2023, rising to more than 2,000 cases by late 2024.

Why SIM takeover fraud is becoming more frequent

1. Your phone number could be the gateway to your digital life

Many accounts now rely on SMS-based security codes, making your phone the key to logging in.

2. Criminals just need information, not high-level technical skills

Scammers just need to gather enough personal information to pass security checks with mobile providers.

3. Fraudsters follow where the money is

With more financial services and identity checks linked to mobile numbers, taking over a SIM has become one of the most effective ways for criminals to access money and accounts.

How to know if your SIM has been taken over

The difficult part of SIM takeover fraud is that it often happens suddenly and silently, but there can be warning signs:

1) Sudden loss of signal

If your phone suddenly switches to “No Service” or stops receiving calls and texts, this can be a red flag. Fraud experts say this is one of the most common early indicators of an unauthorised SIM swap.

2) Unexpected messages from your mobile network

This could be a text confirming a new SIM has been activated or an email about account changes you didn’t make. Victims often report receiving a message about a new SIM before everything goes quiet.

3) Locked out of online accounts

If criminals intercept security codes sent by text message, they can quickly reset passwords to log in and lock you out of your accounts – sometimes within minutes.

4) Unauthorised transactions or login attempts

If you receive alerts about banking activity or logins you don’t recognise, this may mean your SIM has been compromised and used to approve transactions.

What to do next if you think you’ve been targeted

If you’ve spotted any of the warning signs above, it’s important to act quickly to prevent fraud from occurring:

1. Contact your mobile provider

Notify them that you think your SIM has been taken over. Ask them to:

• Block any fraudulent SIM activation.

• Secure your account.

• Reinstate your number on your original SIM.

Providers are familiar with this type of fraud and can act quickly.

2. Change your passwords – especially for financial accounts

Update passwords for your online banking and emails and make sure they’re unique.

3. Enable app-based authentication instead of SMS

This will prevent SMS messages being intercepted and used for authentication.

4. Check bank accounts for suspicious activity

Be vigilant for new payments, transfers, or login alerts. Report any unfamiliar activity immediately.

5. Report the incident

You can report SIM takeover fraud to Report Fraud, who track and investigate cases across the UK.

How to protect yourself from SIM takeover fraud

Thankfully, there are several steps you can take to reduce the risk – and many of them are simple habits you can build into your everyday life.

Keep personal information to a minimum online

Fraudsters often use public information to impersonate your identity. Limiting what you share across social media makes it more difficult for them to pass security checks with your mobile provider.

Use strong, unique passwords

Using the same password everywhere makes things easier for criminals – once they have one password, they’ll have them all. Try to use longer, unique passwords that incorporate symbols and numbers.

Turn on account alerts

Many banks and email providers allow you to opt in to login notifications, password changes, and suspicious activity. They should allow you to block login attempts from the device or location associated with the attempt.

To recap

SIM takeover fraud can feel unsettling but understanding how it works and how to prevent it can make a huge difference. What matters most is responding quickly and taking preventative steps to secure your accounts going forward.

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