Advice · 4 min read · Updated 6 November 2026
Does a factory reset delete everything? 7 data wiping myths busted
Myth 1: Deleting files removes them
When you delete a file, the operating system marks the space as free but the data stays on the disk until something overwrites it. Emptying the recycle bin does the same. On a traditional hard drive, recovery software can often restore deleted files in minutes, which is why second-hand drives bought online regularly turn up full of old business documents.
SSDs behave a little differently because of a feature called TRIM, which can clear deleted blocks in the background. That makes recovery harder, but it is not guaranteed, it depends on the drive and operating system, and it gives you no evidence either way.
Myth 2: Formatting a drive wipes it
A quick format rebuilds the file system and leaves the data in place. A full format in recent versions of Windows does write zeros over a hard drive, which is much better, but it gives you no report, no verification and no record you can show an auditor. On SSDs, formatting may not reach spare areas of the memory at all.
Formatting also does nothing for data held outside the main drive, such as a second drive in a desktop, a recovery partition or an external backup disk plugged in by the user. Erasure needs to cover every storage device in the machine.
Myth 3: A factory reset is always enough
On a modern iPhone, or an Android phone with encryption turned on, a factory reset destroys the encryption key, which makes the old data unreadable. Laptops with BitLocker or FileVault enabled behave similarly when reset properly. On older devices, unencrypted laptops, printers and some tablets, a reset can leave data recoverable.
The other problem is evidence. A reset done by a staff member leaves no record of who did it, when, or whether it worked. For a business, a reset is a sensible first step but not proof of erasure.
Myth 4: You need seven passes to wipe a hard drive
Multi-pass methods such as the old US DoD three-pass and the 35-pass Gutmann method were designed for much older drive technology. Current NIST guidance treats a single overwrite, followed by verification, as enough to clear a modern hard drive. Extra passes add hours without adding real security. What matters more is that every sector, including hidden areas, is reached and the result is verified.
A single verified pass on a typical laptop hard drive can take an hour or more, so multiple passes across a large fleet waste days of work for no extra benefit.
Myth 5: Drilling a hole destroys the data
A hole through a hard drive platter makes it unusable in an ordinary computer, but most of the platter surface remains intact and could in theory be read by a specialist lab. On an SSD, a single hole may miss most of the memory chips completely. Shredding to small particles, or verified software erasure, is far more reliable than DIY drilling or hammering.
DIY destruction also creates a safety risk, from flying fragments and damaged batteries in laptops, and still leaves you without a certificate listing which drives were destroyed and when.
Myth 6: Degaussing works on any drive
Degaussers use a strong magnetic field to scramble data on magnetic media such as hard drives and tapes. They do nothing to SSDs, USB sticks, memory cards or the flash storage inside phones and tablets, because these store data electronically. Degaussing also leaves a hard drive unusable, so it cannot be resold.
Degaussers also need to be powerful enough for modern high-density drives. An older or under-specified unit may not fully erase a recent hard drive, so ask any provider which degausser they use and how they check its effectiveness.
Myth 7: Broken devices are safe
A laptop that will not boot, or a drive that has failed, usually still has readable data on it. Recovery labs routinely get data off failed drives. Broken and faulty kit should go through the same process as working kit, which normally means physical destruction if software erasure cannot run.
| Method | Removes data reliably? | Gives evidence? |
|---|---|---|
| Deleting files | No | No |
| Quick format | No | No |
| Factory reset on encrypted device | Usually | No |
| Certified erasure software | Yes, when verified | Yes, per device report |
| Shredding to small particles | Yes | Yes, with serial numbers |
Frequently asked questions
Is it safe to sell an old work laptop after a factory reset?
If the laptop had BitLocker or FileVault turned on and you used the built-in reset with the option to clean the drive, the data is very unlikely to be recoverable. Without encryption it is less certain. For a business, use certified erasure software so you have a report showing the device was wiped before it left your control.
What is the safest way to wipe an SSD?
Use erasure tools that issue the drive's own sanitise or secure erase commands, ideally with cryptographic erase, and verify the result. Ordinary overwriting may miss spare areas of the memory that the computer cannot see. If the drive is faulty, will not accept the commands, or the data is highly sensitive, shredding to small particles is the safest option.
Do I need a certificate for every device?
For business equipment it is good practice. A certificate or erasure report listing the serial number, method, date and result lets you prove to the ICO, auditors or customers that personal data was destroyed. A single certificate saying a batch of equipment was wiped, with no serial numbers, is much weaker evidence because it cannot be matched to your asset register.
data erasure factory reset myths data security
