The big fight is on TV on Saturday night but you really don’t want to shell out to watch it on pay-per-view. Luckily, you bought a cheap Amazon Fire Stick online that gives you access to all the sports you want as well as TV streaming services.

While the quality of the picture is not brilliant, you are saving on monthly subscriptions and the one-off fees to watch big sporting events. The stick was a bargain – or so you think.

In fact, using a “modded” Amazon Fire Stick in your laptop or TV can give criminals an open door to your bank details and passwords, putting you at risk of losing thousands and having your identity traded over the web.

A recent survey from BeStreamWise, a UK initiative established to counter the problem, found two out of every five people who used illegal streaming were defrauded. They lost an average of almost £1,700 each as a result.

“Illegal streaming might look like a quick way to save money, but … it’s a false economy that can end up costing people thousands,” says DCI Emma Warbey of the police intellectual property crime unit (PIPCU) at City of London police.

“This is a crime that diverts funds away from the entertainment industries – money that supports thousands of technical and support staff. At the same time, it exposes end-users to the risks of data theft, cybercrime and fraud.”

The modded or “jailbroken” devices are Amazon Fire Sticks with extra software added that can be bought for about £20 on the internet.

The growing use of them has led to a crackdown by the Federation Against Property Theft (Fact), which has been carrying out raids across the UK to stop supply.

In one case, according to BeStreamWise, a man who was streaming illegally had his bank details stolen twice and someone tried to buy a boat in his name.

What the scam looks like

The sticks are sold through social media and illegal streaming sites, often advertised as being jailbroken with promises of free TV shows, sports and films.

The potential for fraud happens the minute you put the “dodgy stick” into a laptop or TV, according to Rob Shapland of Cyonic Cyber, an ethical hacker who shows companies where there are gaps in their security systems.

“Alongside the stream [of TV or sports] it will also install some malware on to your computer and give the criminal direct access to your computer so [they] could use it as if they were sitting there,” he says.

“Or they can install keyloggers which will record any password you are typing. So when you are accessing online banking, it will record your banking passwords. You are essentially volunteering to have your laptop hacked in many cases.”

Often the stick will come with instructions which appear to be how to install the software but are actually ways to bypass virus detectors.

When you plug the device into a TV, it can access other devices, such as laptops, through the home wifi network that they are all attached to, says Shapland.

“It might ask you to log in with your Google account and then you are giving your credentials to the app and that is then sent off to the criminals. Most people tend to reuse the same password so once they have one password, they have access to a hundred different things.”

Some sticks may ask for a small monthly subscription. Setting up the payment means criminals can use your credit card details in any way they want.

What to do

Once you know that the device you are using is illegal, you should remove it from your devices immediately.

The next step is to change the passwords on any important sites and apps – such as banking, investments, pensions and PayPal – says Shapland. Turn on multifactor authentication to bolster security.

Undo any changes to anti-virus software made by the software on the stick. Then run a virus scan, available for free online, on your laptop.

If you have been defrauded, it is likely that the damage was done when the stick was first plugged in, says Shapland.

In the UK, contact Action Fraud, the national fraud reporting centre, and report what happened to your bank.

Amazon said people had been convicted in connection with the sale of modded devices and the company would continue to work with the authorities to stop the sales. “Piracy is illegal, and customers should not buy these devices,” said the company.