[Filligree]

I won't say it's completely impossible, but modern HDD read heads are already close to our technical limit, and the signal they get is so noisy as to require extensive processing.

There definitely was a period where labs could recover data this way, but I think it's passed.

[Johnny555]

Hard drives automatically remap bad sectors, so even if you overwrite 100% of the accessible data, you may still have left pieces of data in remapped sectors that weren't overwritten. If your drive supports the SECURITY ERASE feature, then it should overwrite those blocks too.

Though if you really want to sell or give your drive to someone else, the best thing to do is to use full disk encryption from the beginning, then there will be no plain text data on the drive.

[cmurf]

And that's probably why the single pass of zeros is considered adequate, and why a single pass ATA Secure Erase or Secure Erase Enhanced is better than that.