A study shows that the majority of computer users don’t take enough precautions when disposing of their USB sticks, leaving often sensitive information about themselves for the drives’ new owners.

Researchers from the University of Hertfordshire purchased 200 second-hand memory sticks – 100 in the United States, 100 in the United Kingdom – on the open market recently to see how many of them still contained data from previous owners.

They found that most USB drives contained leftover data from previous owners, and the information could be retrieved with zero or minimal effort, reports Comparitech, which had commissioned the study.

Specifically, 20 people made no attempt whatsoever to cleanse their storage devices. Simply plugging the memory sticks into a computer was enough to reveal their contents.

Although the data was deleted, publicly available data-recovery software could be easily restore the contents of 135 thumb drives with little effort, even where they had been formatted. Of those, 44 USB drives contained enough information to identify the devices’ previous owners.

The data found on the thumb drives was everything from corporate and legal documents, tax forms, photos of money and shotguns together with a search warrant, as well as nude images of a middle-aged man along with his name and contact details.

Meanwhile, only 34 USB flash drives were securely wiped with dedicated software while only one was encrypted, putting whatever data that was ever stored on the sticks beyond reach for the new owners.

Simply dragging files into the trash can or highlighting them and hitting the “Delete” key does not permanently erase data from a USB drive. Similarly, formatting a USB drive still leaves recoverable remnant data. To fully erase data, it the storage area containing it must be overwritten, preferably by secure data erasure software.