It seems the most obvious thing to do when you reach your hotel, or you have a couple of hours to kill at an airport while you wait for your connection – find a charging point and plug in your mobile phone.

But now the FBI is warning visitors to the US to be aware of their “cyber hygiene” and avoid public charging stations, highlighting that they may be targeted by what they refer to as “bad actors” willing to access personal data or introduce malware and spyware on to travellers’ devices. It is warning users not to charge devices using free charging stations in public areas that offer a USB connection.

The USB plugs can get access to files stored on a phone or laptop, so anything plugged into the port, such as a charging wire or USB thumb drive, is able to steal information or take over a device.

A statement released by the FBI in Denver read: “Avoid using free charging stations in airports, hotels or shopping centers. Bad actors have figured out ways to use public USB ports to introduce malware and monitoring software onto devices. Carry your own charger and USB cord and use an electrical outlet instead.”

The FBI is also warning against using public Wi-Fi networks to access private information or to carry out financial transactions, adding: “Do not conduct any sensitive transactions, including purchases, when on a public network.”

Signs that your device may have been infected include losing battery life quickly and overheating, with spyware also able to slow down the operational speed of your phone.