Friday, December 3

Juice jacking: why you should be very careful when recharging your mobile in public USB ports and how to avoid problems

Our dependence on mobile phones has caused us to often find ourselves in that dreaded situation in which we are about to run out of battery.

To alleviate the problem many public places such as restaurants, trains or airports offer USB charging ports, but be careful, because using them without taking some previous precautions can be a very bad idea.

When ports do more than load

Theoretically, these charging ports are an excellent idea, and allow that in a hurry we can recharge the device to be able to use it normally again.

The problem is that these public ports are accessible to everyone, and that means that cybercriminals can take advantage of that free access to modify them and turn them into ports capable of installing malware while we are charging those devices.

The same goes for cables almost carelessly connected to these ports, as if someone had left them there. Using those cables is also dangerous, and it can lead to serious problems for our data and our device.

This technique is known as juice-jacking, a term coined by the security expert Brian Krebs in 2011 and allows, as we say, a cyber attacker to install malware on your devices, in addition to being able to modify those ports to achieve copy sensitive data from our mobile such as passwords or personal information.


In a USB 3.0 port we have the four traditional pins (at the top), while we also have pins for those higher transfer speeds (SSTX refers to SuperSpeed ​​transmission and SSRX to SuperSpeed ​​reception).

The operation of this technique is simple if we consider that a USB port does much more than a port to recharge our mobile: these connectors have four pins as a base -although more recent versions have increased this configuration while maintaining the originals-, of which two are used to recharge a device and two others for data transfers.

Dodging the problem

It is not highly recommended to use these ports to recharge the device unless we are very needy, but if we have no alternative we must make sure that when we connect them the data transfer option is not activated of our device.


So, you have to have the charging option active without further ado, something that is the default option in Android, but just in case it is convenient to verify when we connect these devices to one of these ports.

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It may be that when connecting the device to the port on the screen of that device a message will appear asking us if we trust that device. You always have to answer no to that question, if it appears on a public USB port, it should actually make us suspect that something strange is happening there.

Safe recharges away from home

Fortunately when it comes to recharging our mobile devices numerous alternatives have been appearing that allow not having to depend (at least not totally) on finding a public port in which to recharge the device.


Among them is of course that of carry an external battery that allows us to recharge the mobile in these situations. There are many and very diverse models with very different capacity and power delivery, so that we can choose from small 5,000 mAh models to more designed batteries for long trips that usually have 20,000 mAh capacity or more.

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The other option is to take with us our own adapter / charger, which can be the same one we use at home or it can be an auxiliary one. It is even interesting to acquire an additional one that may not load as fast as the official one of our mobile or tablet, but we do recommend that it have a striking option if we use it out of face: overload protection, which prevents problems when connecting to sockets in public places.


There is another curious element in this area: USB “condoms” which are small adapters with a male and female USB-A connection that basically block the possibility of data being transferred through them, but that do allow current to pass through. They are an equally interesting option to be able to use the public charging ports without fear that they will steal data or install malware from them.

If our device has wireless charging We can always choose that option as well, either with a charger that we connect to those public ports – and that they will not be able to transfer data – or with another device that has reverse wireless charging, something that is gradually available in some high-end devices.

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