Deleted Isn't Gone: Why Most Second-Hand Hard Drives Still Hold Data

Most people know they should wipe a computer before getting rid of it. Most of them try. A well-known study shows that trying isn't enough.

What the study found

Researchers at the University of Hertfordshire, working for Comparitech, bought 200 second-hand hard drives online and from merchants and checked what was left on them. As summarized by ESET's WeLiveSecurity:

  • Almost 60% of the drives still held the previous owner's data.

  • Only 26% had been wiped properly.

  • 1 in 6 owners hadn't tried to wipe the drive at all.

  • Recovered files included passport scans, bank statements, and tax documents.

Look at those numbers together. Most of the owners made some attempt to remove their data. They just used methods that didn't work.

Why deleting and formatting fall short

Dragging files to the trash doesn't erase them. It removes the pointer to the file, and the data itself often stays on the drive until something overwrites it. A quick format works the same way: the drive looks empty, but the contents can often be recovered with widely available tools.

For a business, school, or university, one improperly wiped drive can expose employee records, student information, or customer data. Multiply that across a fleet refresh and the risk grows quickly.

The study is from 2019, and drive technology has changed since then. The takeaway hasn't: data is only gone when it has been erased properly and verified, or when the drive has been destroyed.

What proper data destruction looks like

At RePower, every device that comes through our Buffalo Grove warehouse gets the same treatment, whether it has resale value or not:

  • NIST 800-88 certified data erasure verified, with a serialized certificate of erasure for every job

  • Physical destruction when a drive can't be wiped

  • R2 certificates of destruction provided

We process about 25,000 devices a month and accept any IT equipment in any condition. We pay for items with resale value. Items without it still get secure data handling and are recycled responsibly.

Don't leave your data to chance

If your organization's current process is "delete and format," or if nobody is quite sure what the process is, now is a good time to fix it.

Send us your equipment list and get a free quote within 24 hours, or call (224) 360-1500 (8 AM–4 PM CT, Monday–Friday). RePower, LLC · 1692 Barclay Blvd, Buffalo Grove, IL 60089.