Flash drives are difficult to erase safely

Think you’ve deleted those confidential documents from your USB flash drive? Think again.

New research has discovered that Solid State Drives (SSDs), both large internal SSDs replacing hard drives and ubiquitous portable USB flash drives, are much more difficult to erase than hard drives. In fact, if using secure erase tools designed for hard drives, the files may never be deleted.

This revelation has worrisome implications. USB flash drives have become the preferred medium for transporting files. They are smaller and more durable than floppy disks or CD-R/DVD-R disks, and reusable. Solid State Drives (SSDs) are becoming more common in laptops, due to their many advantages over hard drives including faster access, greater reliability and lower power consumption. SSDs are on the way to become the primary storage medium, so clearly they will be used for confidential or sensitive data.

Securely deleting data from hard drives can be achieved using secure deletion tools. Such tools are now common, and often come as part of other software. Researchers found that such tools do not securely delete from SSDs.

The reason that hard drive deletion tools aren’t effective on SSDs is due to differences in how data are stored. Hard drives write data magnetically to a physical location on the metallic drive platter. SSDs store data digitally to computer chips. When data are modified, the SSD often writes brand new files to new locations, leaving the previous version intact.

When hard drive secure deletion tools are used on SSDs, they are likely to give false confirmation of deletion. Such software simply wasn’t designed for SSDs.

The researchers concluded that effective data deletion on SSDs requires built-in tools, designed specifically for the SSD. Until then, be careful.

The research abstract and full paper are available.