Charging your phone in public

The concern

A USB port can carry data as well as power. Security agencies, including the FCC, have warned that a tampered public port could in theory try to install software or copy data from a phone, sometimes called juice jacking.

Real cases are rare, and modern phones ask before sharing data over USB. Still, a few habits remove the risk entirely.

Safer ways to charge

• Use a wall outlet with your own charger instead of a built-in USB port.
• Carry a portable battery pack and charge from that.
• Use a charge-only cable or USB data blocker, which passes power but not data.
• Use your own cable. Do not use cables left plugged in at charging stations.

If your phone asks a question

If you plug in to charge and your phone asks whether to trust this computer or allow access to data, choose Don’t Trust or Charge only. A charging station has no reason to ask for data.

Keep the phone itself protected

• Keep it updated, since updates fix the kinds of flaws these attacks would rely on.
• Use a screen lock, so a phone left charging cannot be opened by someone nearby.