Shocking new pictures reveal criminals are hiding pin-sized cameras in cash machines to record people's bank card numbers.

The cameras have been spotted in locations across central London, with the last one found within the last few days. 

It was hidden inside a fake cash-dispensing slot cover, recording the keypad as people entered their details.

Two were found at ATMs in St Paul’s Churchyard within weeks of each other – one on February 18 and one on March 7.

ATM fraud: five signs a cash machine has been tampered with

Photo credit: City of London Police

Others were found by members of the public on nearby Smithfield Street on March 8 and on Fetter Lane on March 2.

What can I do?

Police are telling people to stay sharp when they’re getting cash out: always cover your hand when you enter your Pin.

Fraudster's camera bar recovered from an #ATM near @StPaulsLondon. Please remember to cover your pin when using a cash machine. #CrimeSquad

— City Police (@CityPolice) March 13, 2017

Before you even enter your details, check the cash machine for loose parts, including the card slot and keypad.

PC Matt Clarke from the City of London Police Crime Squad said:

“We work closely with banks, building societies and other cash machine vendors to make sure this type of crime doesn't happen.

“If you spot anything unusual about a cash machine, or if there are signs of tampering, don’t use it. If in doubt, try and use a machine inside a branch.”

ATM fraud: five signs a cash machine has been tampered with

Photo credit: City of London Police

“If you spot a suspicious device when using a cash point, report it to the bank concerned immediately and notify police. If you think a crime is in progress when you discover the device, call 999.”

Don’t try and remove the camera yourself as the criminals in question could be hanging around near the machine and might confront you.

These are far from the only cases of ATM tampering. Take up the following tips to suss out whether your cash machine has been compromised, courtesy of software firm Fico.

Fake fronts

In some cases criminals place card or cash capture devices and Pin compromise devices in or around ATMs to get quick access to your cash.

A few sneaky scammers will even put on entire false fronts to capture unsuspecting people’s PINs and money, Fico told This is Money.

They’re often really well disguised so have a thorough check of the ATM before you start using it.

ATM fraud: five signs a cash machine has been tampered with

Photo credit: Fico

A wider card slot than normal

You’re right to be concerned about an unusually bulky card slot, as this could contain a ‘skimmer’.

This tool is attached to the ATM’s card slot that secretly takes your card details when you’re making a withdrawal. Apart from its width, it’s really difficult to distinguish it from a normal card slot.

Keep an eye out for misaligned or misprinted stickers - it’s often an attempt to cover up where a compromise device has been installed.

ATM fraud: five signs a cash machine has been tampered with

Photo credit: Fico

A loose or blocked card slot

This may be a sign of a ‘Lebanese Loop’. Criminals will try and trap your card in the machine by placing a tiny plastic device or sleeve with a barb into the card reader so that when you try and withdraw money, your card will get stuck.

ATM fraud: five signs a cash machine has been tampered with

Photo credit: Fico

The ATM will keep asking for a Pin as it can’t read the card, leading you to believe that your card has been swallowed and walk away. That gives the fraudsters the perfect opportunity to swoop in and take your card.

Loose Pin pad

Be wary if the Pin pad feels loose, thick or sponge-like. This crafty trick is known as ‘pin-pad overlay’  the real Pin pad is covered by a fake which does record your PIN correctly just like any other machine, but also captures your details for the fraudster.

In some cases numbers are instantly transferred by WiFi to a waiting accomplice so that they can record it and use it later.

[Read more: Six vital consumer rights to stop you being ripped off]

Loitering groups of strangers

This warning is nothing new but is still vitally important: be aware of what’s going on around you. Don’t accept help from strangers and don’t allow yourself to get distracted.

Scammers often work in teams and they rely on distraction to catch their victims out.

It's a good idea not to use cash machines near a group of people who are inexplicably loitering. If something goes wrong they may become oddly helpful and when one is trying to assist you, the others may look at your PIN or swipe your card or cash.

More on scams and how to avoid them