There is a lot of evidence that contradicts your claim. According to the 2006 NIST Special Publication 800-88 Section 2.3 (p. 6): "Basically the change in track density and the related changes in the storage medium have created a situation where the acts of clearing and purging the media have converged. That is, for ATA disk drives manufactured after 2001 (over 15 GB) clearing by overwriting the media once is adequate to protect the media from both keyboard and laboratory attack." The National Institute of Standards and Technology is a government agency that makes recommendations to government and industry. Secure data erasure is important, for example, to comply with HIPAA, the medical privacy law. Hospitals must destroy medical records when their computers are decommissioned. They must wipe their hard drives. If they threw away a bunch of computers with insecurely erased hard drives and someone was able to recover patient records, that would be a massive violation of federal law. That's why it's unlikely that NIST is lying about their recommendation in order to screw us. According to the 2006 Center for Magnetic Recording Research Tutorial on Disk Drive Data Sanitization Document (p. 8): "Secure erase does a single on-track erasure of the data on the disk drive. The U.S. National Security Agency published an Information Assurance Approval of single pass overwrite, after technical testing at CMRR showed that multiple on-track overwrite passes gave no additional erasure." Again, this Information Assurance Approval by the NSA is for other government agencies. They are unlikely to be lying to them. I posted the entire CMRR white paper here: http://dkn255hz262ypmii.onion/index.php?topic=99520.msg699299#msg699299 Further analysis by Wright et al. seems to also indicate that one overwrite is all that is generally required. http://link.springer.com/chapter/10.1007%2F978-3-540-89862-7_21 Perhaps the best evidence that the NSA doesn't have magic technology to recover files after random writes is this: A forensics expert testified in the Bradley Manning trial that, "the hard drive on Manning's computer had been securely erased in January 2010. "Everything from early January is gone"'. http://www.theguardian.com/world/blog/2011/dec/19/bradley-manning-pre-trial-hearing-live-updates Bradley Manning is the highest profile person to be prosecuted by the US government in the last 5 years. If they had the ability to recover data from his computer after it was securely erased, they would have used it. They didn't use it because it doesn't exist. Or if it does exist and Manning wasn't worth the trouble of using it on, none of us are either. I should point out that Manning tried several times to securely erase his hard drives. One of those times was a zero write and they were able to recover data from that, so we should consider zero writes to be insecure. However, one random write is sufficient to make data unrecoverable.