There’s nothing more intriguing than finding a random USB drive while cleaning up your office or while out and about. You might feel the urge to plug it in and discover its contents, but we are here to tell you that this is often a bad idea—particularly if the drive is unfamiliar to you. Unlike cloud storage, which is quite transparent, you don’t know what’s on a USB drive until you plug it in, and it’s often too late by the time this happens.