Every so often, we receive an email that stops us cold. Not because it is dramatic. Not because it is careless. Because it feels impossible. 

Sheri M. from Georgia recently wrote to us with this question:

“Yesterday I learned that someone had stolen my debit card information. I was alerted by my bank about 10:00 p.m. last night that someone tried to use my card in Brazil. I am in the Southern United States and have never traveled outside the country. What I have trouble understanding is that this particular debit card has never been used and has never been out of a locked vault. It has been activated, and once activated, I locked it up. No one had access to it, no questions about that. It is just not possible. So how could someone have my card information? I asked this question at my bank, and after speaking to several people, they are at a loss as to what to tell me. I hope you can shed some light on this.”

— Sheri M. from Georgia

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Sheri, first, we are glad your bank flagged it. That alert tells you fraud monitoring worked. Now let’s address the part that feels unreal. How can someone use a debit card that has never left a locked vault?

If you have asked that same question, you are not alone. This type of debit card fraud happens more often than most people realize. And it almost never involves someone physically touching your card.

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How debit card fraud happens without using the card

When a card is compromised without being used, the issue is typically digital. Here are the most likely explanations.

1) The number was exposed before you received it

Debit cards move through multiple systems before they reach your mailbox. Third-party vendors manufacture, encode and ship them. That means the card number exists in databases long before you open the envelope. If one of those systems is breached, criminals can obtain card numbers in bulk. They never need the physical card. They never need your home. In that case, it has nothing to do with your vault. 

2) A BIN attack may be responsible

Every debit card starts with a bank identification number. Criminals use software to generate the remaining digits at high speed. They test thousands of combinations using small transactions or foreign authorizations to see which numbers work. This is known as a BIN attack. They are not stealing your specific card. They are guessing valid numbers mathematically. If your card was activated, even if it was never used, it becomes part of the pool that can be tested. A foreign attempt, like one in Brazil, is often a test authorization. It feels personal. In reality, it is automated. 

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A customer completes a transaction at Pike Place Market in Seattle, Washington, on May 28, 2025. Financial security specialists recommend canceling compromised cards and monitoring accounts immediately after a fraud alert. (M. Scott Brauer/Bloomberg via Getty Images)

3) A processor or network weak point

Sometimes the exposure does not originate at the bank itself. The weak link can involve:

• A payment processor
• A card network
• A digital wallet backend
• A servicing vendor

Frontline bank employees often do not have visibility into these system-level issues. Patterns can take time to surface internally. That is why you may not receive a clear explanation right away. 

4) Backend systems assign numbers early

Many banks pre-assign card numbers or connect them to digital systems before you ever swipe the card. If that backend data is exposed, the physical card remaining locked away does not matter. That is why debit card fraud without using the card can still occur.

Why did the transaction show up overseas?

You may wonder why the attempt came from Brazil. Foreign authorizations are often used as test transactions. Criminal groups run small or unusual location charges to see which numbers are active. If the charge clears, they escalate. The good news is your bank blocked it. 

What you should do right now

If this happens to you, act quickly.

• Cancel the card completely. Do not just lock it. Make sure the number is permanently closed.
• Request a new card number. Confirm it is not a reissue of the same digits.
• Monitor your checking account daily for at least 30 days.
• Freeze your credit with all three credit bureaus.
• Add identity monitoring to detect broader misuse.

That final step is often overlooked.

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Experts say debit card fraud often occurs without the physical card ever being used or stolen. (Nikos Pekiaridis/NurPhoto via Getty Images)

Why identity monitoring matters

Debit card fraud can be isolated. It can also signal a larger data exposure.

If your card number surfaced through a breach or vendor leak, other personal details may be circulating too. Email addresses, phone numbers and Social Security numbers often appear together in stolen datasets. That is where early detection becomes critical.

Our top Identity Theft Protection recommendation monitors credit activity, financial accounts and dark web marketplaces for signs your identity is being misused. You receive fast alerts so you can respond before small incidents turn into larger problems.

Instead of waiting for a late-night fraud alert, you gain earlier visibility.

See my tips and best picks on Best Identity Theft Protection at Cyberguy.com.

Ways to stay safe from invisible debit card fraud

You cannot control global criminal networks. You can reduce your exposure.

• Keep debit cards locked in your banking app when not in use
• Turn on real-time transaction alerts
• Use credit cards for online purchases when possible
• Freeze your credit as a preventative step
• Avoid storing debit card details across multiple retail sites
• Use identity monitoring for broader protection

Layered security gives you more control.

Kurt’s key takeaways

Sheri’s experience feels impossible because she did everything right. The card never left the vault. It was never used. No one had access. Yet the number was still tested from across the world. That is the reality of today’s financial crime. It is automated, remote and system-driven.

If this can happen to a card locked in a vault, what does that say about how secure our financial system really is? Let us know by writing to us at Cyberguy.com.

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It sounds like the opening of a sci-fi film, but US scientists recently uploaded a copy of the brain of a living fly into a simulation. In San Francisco, biotechnology company Eon Systems created a virtual insect that knew how to walk, fly, groom and feed in its virtual environment. Researchers in Australia, meanwhile, have taught a petri dish containing 200,000 human brain cells to play the iconic 90s shooter Doom. One experiment has pushed a brain into a computer; the other has plugged a computer into brain cells.

Both stories have been hailed as scientific breakthroughs, but have also sparked inevitable fears about the prospects of lab-grown humans and digital clones. Should we be concerned?

It was Australian startup Cortical Labs in Melbourne that taught a dish of lab-grown neurons to play Pong in 2022. Now it has built what it describes as “the world’s first code-deployable biological computer”, running on living human tissue rather than silicon chips, which is happily playing the 1993 shooter Doom.

“In computer-science nerd land, there’s this obsession with getting Doom to run on everything, from calculators to microwaves,” Hon Weng Chong, CEO of Cortical Labs, tells me over Zoom from Melbourne. “As soon as we managed to get Pong to work, the first thing people said was: ‘When are you going to do Doom?’”

The average human brain contains about 86bn neurons – roughly 430,000 petri dishes’ worth. But how do you harvest 200,000 brain cells without resorting to a hacksaw and an ice-cream scoop?

“They’re my brain cells, actually – at least most of them are,” Chong says proudly. “There’s no scraping or brain extraction. It’s a very cool technique that was developed by Professor Shinya Yamanaka, who won the Nobel prize in 2012.”

All you need is 10ml of blood (in this case Chong’s), from which around 100 white blood cells can be harvested. These can then be reprogrammed into induced pluripotent stem cells (iPSCs) – the body’s biological building blocks – which can then be reproduced exponentially.

“Essentially we reverse the biological clock back to an embryonic state, induce them into neurons, and put them on a glass chip roughly the size of a 50p piece,” explains Chong . “Because they’re on a chip – and electricity is the common language between neurons and the computer system – we can interface with them and get them to play Doom.”

Cortical Labs conducted its Pong experiment in-house, but this time it reached out to 24-year-old Singaporean Sean Cole, who has just completed an MSc in artificial intelligence at the University of Sussex, and whose dad happens to be mates with its CEO. Cole wrote the code remotely, which the team then tested on their local machines.

“I was a bit surprised it worked the first time around,” he tells me over Zoom.

So how does a petri dish of brain cells play Doom when it doesn’t have any eyes? Or fingers? “We take a snapshot of the game with information like the player’s health and the position of enemies, pass it through a neural network, convert it into numbers, and send the data,” explains Cole. “This is called encoding – essentially turning the game state into signals the neurons can understand. The neurons then fire an output – move left, move right, walk forward, shoot or not shoot – which the system decodes and converts back into actions in the game.”

“If you think about how humans operate, we have information going into our retina, which is converted into electrical signals, processed in the brain, and then an output happens,” adds Chong. “It’s really no different from that.”

If a computer full of brain cells is playing a video game and making decisions, does that mean it’s sentient? Or is it just behaving like the average Doom player? “People have different perceptions of what sentience is,” says Cole. “I definitely don’t think it’s conscious. At first it didn’t know how to move, aim or even shoot. Then it would shoot the first two enemies and stop – almost as if it was preserving itself. So it’s definitely learning. We’ve managed to control a brain to learn in a very controlled environment. The next step could be something like Neuralink, where you inject a chip into the brain to train someone to learn a language faster.”

Exactly how the cells are learning to play the game is unclear. “We can hypothesise that it might involve things like the free energy principle – the idea that living systems act to minimise free energy – or Hebbian learning, where connections between neurons strengthen when they fire together.” Could we ever use technology like this to instantly learn kung fu, as in The Matrix? “If we find a way to safely connect this technology to humans, that is kind of what the implications might be,” Cole says. “A big concern would be: what if you override someone’s memories?”

While Chong says he’d like to try getting the neurons to play Pokémon next, the real future application here lies not in getting trays of human neurons to graduate to playing Minecraft or Grand Theft Auto, but in medicine. “People are looking at it from biomedical research angles, for disease modelling,” he says. “Things like epilepsy, where drugs could be tested on neurons grown outside the body – not just to discover new drugs, but to tailor them at a personal level.”

Meanwhile, in San Francisco, where Eon Systems has scanned a fruit fly brain and recreated it as a virtual insect, the big scientific news is that the team have essentially recreated the creature’s behavioural wiring. The digital insect already knew how to behave like a fly, without any training or prompting. This challenges a central assumption of modern AI: that intelligence must be acquired. In the case of the fly, much of its behaviour appears to be built-in.

“The brain was scanned using electron microscopy. Our head of engineering led a project to emulate that brain, and now we’ve placed the emulated brain back into a body, so it can wander around a virtual world,” Michael Andregg, CEO of Eon Systems, tells me.

A fruit fly’s brain comprises around 140,000 neurons – about five petri dishes’ worth. The virtual fly has 87 joints and can do pretty much anything an actual fly can. But does it realise it’s living in a simulation?

“The fly probably knows something’s off, because we’re not simulating the environment with high fidelity,” says Andregg. “We can’t give very specific taste and smell cues – just that something smells sweet or tastes bitter, but there are no complex aromas.”

Brain emulation, Andregg suggests, could eventually allow humans “to flourish in a world with superintelligence. Our goal is to make the emulation and computed brain and body feel indistinguishable from the natural biochemical body and brain,” he continues. “If it feels different, we’ve done something wrong.”

But we’re still a long way from the upload-yourself-into-the-internet futures imagined in Devs or The Lawnmower Man, mainly because, in this case, the fly’s brain had to be removed from the body first. “Scanning the body was too hard,” says Andregg, which will probably reduce the waiting list for human volunteers willing to try out the technology.

Chong, meanwhile, believes biological computing could achieve things that traditional computing has struggled with. “There’s a thing called Moravec’s paradox, which is well known in robotics: what humans find very difficult, computers find easy, and what computers find difficult, humans find easy,” he says.

“Abstract reasoning, mathematics and language are relatively recent in evolutionary terms, which is partly why computers excel at them. But motor control and probabilistic decision-making are things we’ve inherited through millions of years of evolution. Robots may be very good at solving maths problems, but we’re still trying to build robots that can walk properly.” Biological systems like the fruit fly simulation, he says, might eventually power robots, drones and other machines that need to navigate the messy unpredictability of the real world.

For now, humanity’s first biological computer is busy doing what humans have always done with new technology: playing games. And somewhere in Silicon Valley, a fruit fly is living its second life inside a computer, totally unaware that it is living in the insect Matrix.