Cases of so-called phone spoofing, where scammers ring your home phone pretending to be a bank or the police or another legitimate company or body, are rising fast.
Fraud watchdog Financial Fraud Action UK (FFA UK) says the number of cases doubled in the past year.
This is down in part to a crackdown on another form of telephone scam, known as vishing. This is where scammers call someone and tell them to call them back on the helpline number for the bank.
However, they keep the line open when the victim hangs up so they are still connected. Previously calls could remain connected in this way for up to two minutes, but a crackdown has seen this reduced to seconds.
As a result scammers are turning to the easier alternative of phone spoofing.
How number spoofing works
Scammers use easily accessible technology to change the number that appears on the caller ID display of your phone to a legitimate number from a bank or other organisation.
The fraudsters pose as bank staff or government employees and attempt to persuade you to hand over personal details, passwords and even Pins.
Sometimes they’ll send a text to your mobile phone, which will show up as having come from your bank. Once the payment has gone through you'll receive another message acknowledging the transaction, confirming your belief that it's genuine.
Ofcom is working with international regulators and UK telecoms providers to resolve the problem. Some of the fraudsters are based overseas so it can be more difficult to pin them down. It can also be difficult to track down the cash once it's gone:
“The problem is that money can be moved so quickly” says Giles Mason of Financial Fraud Action UK. “It can move from the victim’s account to several different ‘money mule’ accounts.”
Keep yourself safe
Your bank or credit card company will never ask you for personal details or Pins over the phone, so you should never give it out even if your think that the caller is legitimate.
If you’re asked to move your money because there’s been fraudulent activity on your account, don’t fall for it.
If you’re unsure of the caller’s authenticity you should hang up and ring your bank back on a number you trust, leaving at least five minutes between phone calls. Phone a friend first to make sure the line is clear.
As part of its action, Ofcom is working with phone networks in the UK to minimise the amount of time phone lines stay open.
A spokesperson said: “All mobile operators and major landline providers have been rolling out changes to their phone networks to reduce the time a phone line stays open to a couple of seconds. Figures show that this work is already having a big effect on the number of scams being thwarted."
What you should do if you’ve been tricked
If you fall for one of these scams, let your bank know right away so that it can try to recover your stolen funds.
And don't forget to report it to anti-fraud organisation Action Fraud so that it can be investigated further.