Speaking to The Sun, founder of cybersecurity company TorGuard, Ben Van Pelt, warned of a common cyberattack targeting USB ports - called 'juice jacking'.
'Juice jacking' is when innocent iPhone or Android owners charge their devices through a USB port that has been tampered with.
Dodgy USB ports can be used to wire malware directly into a person's phone, which in turn can be used to steal someone's data - including their bank details.
People are risk in any public space, such as airports, train stations, pubs and even hotels.
But there's a thumb-sized gadget that can stop hackers from accessing your device via a USB - and block them from bank-raiding attacks.
It's a USB data blocker, and they can be found for about £5 on Amazon.
"A USB data blocker is a small device that prevents data transfer when inserted into a USB port, while still allowing power to flow," Van Pelt said.
"Not everyone needs a USB data blocker," he continued.
"But if you frequently use public USB ports and handle sensitive information, I'd say you should get a data blocker for an additional layer of protection."
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USB data blockers are designed to block the pins used for data transfer - but leave the others working.
So they allow power to be transferred but completely block any data, including potential malware.
It's just one of Van Pelt's three tips to avoid 'juice jacking'.
It might be tempting to ditch your travel adaptors and rely solely on a hotel's USB ports.
Or, if you're desperate for charge, you may even overlook the risks of using a USB port in an airport or train station.
But Van Pelt has urged against it, unless you have a USB data blocker.