A startling number of used hard drives sold on eBay expose sensitive information from their previous owners, a new study shows. The information disclosed by these drives includes everything from scanned passports and information from workers with a high level of government clearance to detailed logistics records and internal memos from private companies.

The study, conducted by data erasure company Blancco Technology Group and data recovery company Ontrack, examined some 159 drives sold on eBay's secondary markets in the US, UK, Germany, and Finland. Researchers purchased used hard drives from leading brands including Samsung, Dell, Seagate, HP, and Hitatchi at random. As a part of the study, they asked the sellers whether they had performed proper data sanitization to ensure no data was left behind. Though every seller said they had erased everything, the results told a different story. 

"This demonstrates that sellers are attempting to permanently wipe data and see the importance of this process," the report explained. "However, many are failing to use a fully effective solution."

Using its proprietary data recovery tools, Ontrack was able to recover sensitive information from 42% of the drives. More than 15% of them contained personally identifiable information, including Microsoft Word and Excel files, photos, personal documents, and email files.

The report explained that, for the most part, these sellers erased data by formatting the drive, often passing up on a full format in favor of a quick format, which only overwrites the drive's index but leaves everything else in place. In both cases, quick and full, the formatting process will overwrite data with zeros to remove data, but there's no way to verify that the data is truly gone after formatting. That means data can linger undetected. 

The results from this study were actually encouraging compared with another study: Rapid7 senior security consultant John Frantz bought a variety of devices from regional refurbishing and donation businesses in the Wisconsin area to see how much data was left behind. He found a scant 3% of drives were properly wiped.

The wide range of proper erasure rates shows how inconsistent practices are in the data erasure business. For enterprises, the disposal or recycling of old equipment can be a massive problem of scale. In many cases, enterprises outsource the disposal and recycling of their equipment to refurbishing or reseller outfits. The lesson here is buyer beware: These sellers may be using only rudimentary wiping practices or may not attempt to erase data at all.

"When donating or selling your technology, you should be sure to wipe it yourself rather than relying on the seller to do it for you," Frantz wrote in a March blog post.

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