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Credit card skimmers are hard to spot — here’s how to protect yourself

Wondering why there are charges showing up on your credit card for purchases you never made? You may have fallen victim to a credit card skimmer, a relatively common tool used by scammers to steal your card information without your knowledge. Perhaps the scariest part of card skimmers is that if you don't know how to spot them, they can hijack your information while you're completing what seems like a completely normal transaction at the ATM or gas pump. Luckily, if you know what to look for and have the right tools, you can identify a skimmer before its too late and can protect your credit.

What is a credit card skimmer?

A credit card skimmer is a small, electronic device that can steal your card information. They often look nearly identical to an actual credit card terminal and function similarly as well, acting as a simple magnetic strip reader. Some are somewhat bulky, though don't particularly stand out if you don't know what you're looking for. Security expert Brian Krebs highlighted a number of skimmer devices, which, if you aren't specifically looking for them, appear to simply be a part of a card reader that you've interacted with hundreds if not thousands of times. In a report from CreditCards.com, David Tente, the executive director of the ATM Industry Association, said that modern skimmers "are almost impossible to see, even if you know what you're looking for."

How does credit card skimming work?

Skimmers almost always sit atop existing credit card scanners to intercept or skim your card information before it reaches the machine. When you insert your card into a machine that has a skimmer attached to it, the skimmer reads the card first. It uses a magnetic strip reader to extract card data from the stripe on the back of your card. That stripe contains your credit card number, expiration date and your full name. That's typically enough to process transactions on less-secure online retailers or to create a counterfeit credit card that can be used to make purchases to your account. Some skimmers are paired with hidden cameras or overlaid keyboards that are used to intercept your PIN by capturing your keystrokes, according to LifeLock. That gives a thief all the information they need to rack up some charges on your behalf or withdraw money from your account at an ATM. Even if your card has an EMV chip, as most do now, the stripe still contains your information in order to remain compatible with older systems, per PCMag.

Where are credit card skimmers usually located?

While skimmers can be used on basically any credit card reader, they are typically placed on ones that aren't regularly monitored. That means you're most likely to run into them at a pump at the gas station or at an ATM. According to data from FICO, ATM compromises were up by 8 percent in 2017, a small but still noteworthy increase. Luckily, that was significantly less than the previous jump of nearly 70 percent in 2016 — much of which was the result of a significant influx of skimmer attacks on ATMs at convenience stores. But a slowed increase is still an increase, and suggests that skimmers are still prevalent even with new protections on credit cards.

Likewise, a significant amount of data suggests that gas stations are still popular spots for card skimmers. Pumps in particular attract the illegal strip readers, as many people pay directly at the pump and a considerable amount of traffic can be targeted. Inspectors in Florida identified card skimmers at nearly 1,000 gas pumps across the state last year, a significant uptick from the 650 that were found the year before. Because gas pumps still don't have to be completely compliant with the EMV chips found in modern cards and can still accept payments via simply swiping your card's strip, they continue to be popular targets for scammers to set up strip readers.

In some cases, though they are significantly less common, you may run into skimming rings at restaurants or other businesses where someone takes your card. Typically in these situations, employees will use a skimmer set up at their register or take down your card information while processing your transaction. These scams are rare in comparison to skimmers as they are usually multi-person operations and require more work than simply setting up a barely detectable device and letting it reap people's information.

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How do I spot a credit card skimmer?

Spotting skimmers can be challenging if they are set up properly. Knowing where to look for them, like at ATMs or gas pumps, is a good start. You'll want to keep an eye out for any signs of tampering on the machine. If anything looks out of place, you might want to raise your suspicions about the machine.

Many card skimmers are on the bulky side, as they are designed to slide over the top of existing card scanners. That means in some cases, the stick out more than you would expect. If you notice a larger-than-normal looking card reader or can identify some discoloration — perhaps the scanner looks like it's a slightly different shade than the rest of the machine — then you may want to avoid using it. You might also notice the card reader wiggle if you touch it, suggesting that it might be an additional piece that isn't intended to be there.

It's also worth taking a closer look at the keyboard. If it looks thicker than a standard one or if the buttons feel a little odd, you may be dealing with a keyboard overlay designed to capture your PIN.

Of course, going through your normal routine, you may not give much thought to these things. You're just trying to get gas or withdraw some cash or pay for your order and get on with the rest of your day. Luckily, there are tools on the way that will help do the job of detecting skimmers for you.

Computer scientists at the University of California, San Diego recently released a smartphone app that can detect credit card skimmers. The app, called Bluetana, can identify Bluetooth signals coming from the fraudulent devices. In test runs, the app was able to detect card skimmers in as little as three seconds. Researchers used the technology to identify 42 card skimmers installed on gas pumps in three states — including two such devices that were installed and stealing cards for nearly six months before being detected. The app hasn't been made public yet, but the technology represents a significant advance in stopping these types of scams.

What do I do if my credit card gets skimmed?

If you think your card information was stolen by a credit card skimmer, the first thing you're going to want to do is to contact your bank or card issuer. They will be able to alert you to any charges made with your account that you didn't approve. You can also have them cancel your card to prevent it from being used.

You also may want to raise the issue with the Federal Trade Commission and local law enforcement. They will be able to help with any identity theft protection if you require it. You can also report any information you can regarding where your card may have been compromised so that the proper authorities can investigate and potentially catch the criminals operating the skimmer.