Data shows reported losses for this type of fraud reached more than £16m in the past year.

The consumer champion has heard from people who have lost thousands of pounds to this convincing scam where the perpetrators phone up pretending to be tech support from a reputable firm such as Microsoft or BT.

The fraudster then attempts to persuade the victim to install remote access software – which is used by many legitimate IT workers – that allows them to steal money and personal details.

Which? is calling for banks to refund more customers who fall victim to this sophisticated scam.

It has heard about a number of cases where people have been denied reimbursement due to banks claiming that they either authorised the payments or had been grossly negligent.

Karen, who lives in Brighton and is in her 60s, lost £6,900 in July to a cold caller claiming to be from ‘Amazon Prime Security.’

The scammer quickly created a sense of panic, claiming that her account had been hacked in California. She believed they were helping protect her account and agreed to download TeamViewer, a brand of remote access software.

The fraudsters took over Karen’s laptop and showed her error messages in the Windows Event Viewer program to suggest it was not secure before the screen went black. This gave the scammers an opportunity to access her accounts and steal a total of £6,900 from her bank account and MBNA credit card.

Karen said she ‘felt totally violated’ when the scam came to light. MBNA initially refused to refund her the money but after Which? got involved it agreed to reimburse her in full and pay her £200 compensation.

This is far from an isolated case. In the past 12 months, Action Fraud says it has received 14,893 computer software service fraud reports, with reported losses reaching about £16.5m over that period.

Awareness of this type of technology scam among consumers appears to be low. A Which? survey of the general public in September 2020 found that, despite some banks displaying warnings, four in 10 people have never heard of remote access software.

Based on reports to Which?, TeamViewer is the brand of remote access software reported as being misused by scammers most often, although others include AnyDesk, GoToAssist and LogMeIn.

Providers say misuse of remote access software gives grounds for users to have their accounts shut down. They also told Which? that they monitor accounts for unlawful activity and work with authorities to report abuse.

Although banks must refund unauthorised transactions, Which? is aware of cases where the bank has said allowing remote access to your computer or smartphone amounts to gross negligence and refused to reimburse the victim.

Jenny Ross, Which? money editor, said: “Millions of pounds are lost to computer takeover scams every year, with potentially devastating consequences for victims who lose life-changing sums of money to these callous fraudsters.

“Which? is calling on banks to reimburse all blameless customers who fall victim to these scams and for the government to introduce legislation to ensure a new statutory code of practice can be created, which would include clear standards and protections for victims.

“Anyone who receives unsolicited calls claiming to be from tech support or broadband engineers and asking for personal details or to install computer software should hang up and phone their provider back using the legitimate phone number.”

What to do if you think you’ve given remote access to a scammer

• Switch off both the device and your wi-fi connectivity.
• Speak to your banks as a matter of urgency.
• Remove the relevant app from your list of recent downloads or installed programs, check for other programs that may have been installed remotely.
• Change your email and online banking passwords and, where possible, enable two-factor authentication.
• If you have security software, ensure it has all new and recent updates, then run a full security scan.