USB leeching is the act of recharging a low-powered device such as a camera or cellphone from a powered USB port. This can be authorised or unauthorised leeching.
Why we leech
Portable devices such as digital cameras and mobile phones tend to consume their battery power at a rapid rate. The more you use the device the faster the available battery charge is depleted. You are then faced with the problem of how to restore power to your device. You could carry a spare battery, which can be expensive and requires having somewhere to store the battery when not in use. Or you could just recharge the battery.
The problem with recharging batteries is you need to have your mains charger with you and you have to wait for the device to charge, effectively tying you to the mains outlet making you temporarily immobile.
If your device is a smart phone then chances are that you will be recharging your battery daily if not more often. The more you use your phone, especially if Wi-Fi and/or bluetooth is enabled, the faster the battery will run out meaning it's time for another recharge.
While the fastest way to recharge a portable device's battery is via its mains charger (even faster still if the device is also off during recharging) another way is via its USB cable.
Most portable electronic devices that can interact with a PC come with a USB cable. This cable allows the device to communicate and transfer data with the PC. It also allows the device to make use of powered USB ports in order to (slowly) charge the device's battery.
So rather than having to carry your bulky mains recharging cable you could carry your thin USB cable with you and hook your portable device up to any other device with a power source and powered USB ports.
I myself have a large smart phone that is effectively a palm-top computer that I use for everything from communications and remote working to entertainment. The battery barely lasts 6 hours nevermind a day. I don't carry a spare battery. Instead I carry the phone's USB cable. When I'm at my home office or out on the road and the battery is low it is charging from one of my laptop USB ports (the laptop has a 9-hour battery so it usually has power to spare). When I'm at work it charges from the work PC (please get permission from your employer!).
Others have reported that they have successfully leeched power from USB sockets in other larger USB devices, from Smart TVs and from computers and devices offered free to the public with USB ports available.
Risks and security implications
Of course USB leeching is not without some risks. The first is that you should always seek permission from the owner if you are attempting to leech power from a device that you do not own, especially if you are on private premises or public. Also you should ensure that your device is configured so that when the USB cable is plugged into your device and connected to another that your device does not instantly share whatever data it has stored in its memory. You only want a recharge remember! You don't want to share your data or even information about your device, although that may be harder to lock down.
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Article date: 26th March 2014