What caller ID spoofing actually is
When someone calls you, their phone system sends along a piece of information saying which number the call is from. That information is supplied by the caller's own provider. For most of the phone network's history there has been no reliable way for your provider to check whether it is true.
That gap is caller ID spoofing. A scammer using internet calling software simply tells their provider to present whatever number they like, and that is the number your handset shows. It takes no technical skill and costs almost nothing.
There are legitimate uses for the same mechanism. A hospital with hundreds of internal extensions presents one main switchboard number. A company using an outsourced call centre presents its own number rather than the agency's. The technology is not itself illegal, which is part of why it has proved so hard to shut down.
The three ways it's used against you
Exact number impersonation
The scammer displays the genuine number printed on the back of your bank card. If you check the number while still on the call, it matches — which is exactly the reassurance they are counting on.
Neighbour spoofing
The displayed number shares your area code and first few digits, so it looks like a local business or a neighbour. People answer local-looking numbers far more often than unfamiliar ones.
Burning someone else's number
An ordinary number, often a real person's or a small business's, is used as the display number for thousands of scam calls. The owner then receives angry callbacks about calls they never made.
If people are calling you back about calls you never made
This is the most distressing version of spoofing, and there is no switch that turns it off. Your line has not been hacked and your phone is not infected — someone else is simply displaying your number. Nothing is passing through your account, so your provider cannot block it at your end.
The good news is that these campaigns move on quickly, usually within days or a couple of weeks, because the number stops working for them once it is widely reported. In the meantime:
- 1. Tell your provider. They cannot stop it, but they can log it, and a record helps if the harassment escalates.
- 2. Consider a short outgoing voicemail greeting explaining that your number is being spoofed and you did not call.
- 3. Report it to Ofcom, and to Action Fraud if money has been lost by anyone who was called.
- 4. Do not change your number as a first move. It is disruptive, and the campaign usually ends on its own.
If your number has a page on CallerCheck collecting reports for calls you did not make, you can claim it and ask us to review the reports.
What actually protects you
Because the displayed number cannot be trusted, every reliable defence works by moving the conversation onto a channel you control rather than by inspecting the call.
Hang up and dial back yourself
Use the number on your card, your statement, or the organisation's website — never a number the caller gives you. On a landline, wait a minute or use a different phone, as some older lines can be held open by the caller.
Know what nobody legitimate asks
No bank, police force or government department will ask you to move money to a "safe account", read out a one-time passcode, or install remote-access software. Those three requests are scams every time.
Slow the call down
Urgency is the tool, not a side effect. A genuine caller will accept "I'll call you back". Anyone who argues with that, or warns you not to hang up, is telling you what they are.
Use 159 for banks
Dialling 159 connects you directly to your own bank's fraud team, and it cannot be intercepted or spoofed. Most major UK banks are signed up to the service.
Why blocking the number rarely helps
Blocking works well against a real number that keeps ringing you. Against spoofing it does very little, because the displayed number is disposable — the next call arrives from a different one. Blocking a spoofed number can even be counterproductive if it belongs to an innocent third party you might genuinely need to hear from.
Network-level filtering is more effective. UK providers have been rolling out systems that reject calls presenting a UK number when the call clearly originates abroad, which removes a large share of impersonation traffic before it reaches any handset. On your own device, the practical steps are covered in our guide to blocking unwanted calls.
Frequently Asked Questions
Can I tell if a number is spoofed while I'm on the call?
Is caller ID spoofing illegal in the UK?
My number is being spoofed. Has my phone been hacked?
Should I call back a number that appeared on a missed call?
Does registering with TPS stop spoofed calls?
Quick Summary
On a suspicious call
- • Treat the displayed number as unverified
- • Never read out a one-time passcode
- • Never move money to a "safe account"
- • Hang up and dial back independently
- • Use 159 to reach your bank directly
If your number is spoofed
- • Your phone has not been compromised
- • Log it with your provider
- • Report the campaign to Ofcom
- • Update your voicemail greeting
- • Wait it out before changing numbers