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How To Delete All Data &/or Scrap Old PCs & Devices

This is

by Julian H. Stacey a Computer Consultant

I was asked if these made sense:
  • 2023-01-24 : getpocket . com / explore / item / how - to - completely - wipe - all - data - from - your - computer
    (Their post originally appeared on Popular Mechanics and was published December 13, 2020.) My answer below supplements it, but does Not include text from it, & this is copyright Me, not them.
  • 2023-08-12 : A pay to scrap company Avoid their Entrapment ! Their form mentions no money But you must agree their terms including:
    • Terms 1.2 is garbage legalese off- putting, discouraging reading further, as not Plain English
      But Skim to ...
    • Terms 4: You agree to Pay them to give them your hardware (containing your data) & they could sell your hardware !
    • Best avoid their legal excretia, their entrapment to pay amount unspecified on form, & assignment to them of right to Refurbish & reuse your hardware where they choose.
    Best Erase Data Yourself, Or Scrap It Yourself, Or give it away To Who _You_ Choose


  • ERASE Data

    • Short answer for my local friends: give old machines to me & I'll erase data & use parts.
      Longer answers for public:
    • Realise normal Delete of files & directories on Unix (= BSD, Linux etc) = folders on ( MS = Microsoft) does not delete data off disc. Not even before MS & Android brought in Un-delete boxes. Even flushing your un-delete box won't delete data sectors, it will merely allocate sector numbers as re-usable (as did MS Del command & Unix rm command).

    • To really remove the data, you need to fill the file systems completely with other data. You could do that manually, repeatedly copying loads of bulky junk, & then some small junk, but it's done more easily by my free program testblock (which runs on both Unix & MS, & free source so you can read & trust it not to be spyware).

    • Some MS File Systems don't allow a file to bigger than maybe 2G or 4G, so you may need to open an MS DOS box & run a batch script to create a series of files to fill the file systems. FreeBSD keeps back a default 10% spare disk from normal users, so either pre-use `tunefs -m 0` or run testblock as root. MS may similarly keep back a last so many percent ? Be aware a file system will not be an exact multiple of a testblock default block size, so you will need to finish off filling the remnant with a block size of 512 bytes.

    • A factory reset is insufficient, risky, It can't easily know & may miss where 3rd party programs may have hidden data. It's safer to over write every sector on every disk. That then requires next owner/user of PC to purchase & install their own OS = Operating System. One can get Free OSs from Linux & BSD.

    • Making a backup of your MS OS to an external media, to later recover back after you have completely erased disk will probably fail as the MS recovery programme may likely detect a new system & wrongly bleat copyright theft, aborting. Erasing:
      • MS disk format programs are a misnomer, they merely lay down a new file system structure on the disk. They do Not format all the sectors.
      • Low level disk formatter programs are better. The best way to completely erase is to boot PC from external media, ie a cd or USB stick, then on all disks, run a program that rewrites disk sectors. It may take hours. Such programs often come on a downloadable floppy image from disk manufacturers, or disk controller manufacturers. Occasionally I've seen disk erase built into a few BIOSes. One can also disconnect disk & connect to another PC, & run the erase program from other PC.
      • Data on some (perhaps only older?) disks is recoverable by governments such as spy services & USA NSA that increase amplification & do radial offset reads.
      • One can cut & remove wires between disk PCB & spindle: disk is still readable if re-wired.
      • One can hammer & break the disk PCB: The disk is still readable by using a PCB from another same disk.
      • One can unscrew the aluminium frame of disk (usually one last screw is under label), & remove disk(s), & use as shiney decorations: If cleaned & installed in another same model disk, some data may be recoverable
      • One could also scratch up platters in multiple places, so less sectors are recoverable
      • One could bend/ saw/ melt down / fracture disk platters to prevent remounting in another drive,
      • A short cut for some people would be to unscrew disk drive from PC, place disk on a concrete floor with electronics board upward, label downward & beat it with the corner of a sledge hammer or pick axe. Would also work for SSD (Solid State Disks)
      • It is possible (I've done it) to hide data in remnant blocks beyond the end of file systems, A factory reset is unlikely to know to erase that.
      • It would be possible, if unlikely, for a program to hide small data in the unused flash memory in the end of the BIOS. A Factory reset is extremely unlikely to erase that.
      • Some graphics & other cards have flash-able CMOS for on card extra BIOS, remnant space could there be used for hidden data.
      • Remnant un-erased data: can occur in all of:
        • file system partitions, in last sectors below block size of file system
        • before first BSD disklabel/bsdlabel as boot blocks, & similar in MS
        • unusually, if hidden between partitions within a BSD disklabel/bsdlabel, & similar in MS
        • usually at end of last partition up to beginning of next MBR/fdisk slice, & similar in MS
        • unusually if hidden between MBR /fdisk slices
        • usually after last MBR slice
        • loads of spare sectors, up to half the disk or much more, if disk has had a jumper moved to run in reduced capacity for compatibility with an old BIOS/OS (question would then be was any of your data previously written on there by some other OS, that is now invisible from your PC now running in compatibility reduced mode).
        • Sectors spared out as bad/ irrecoverable by eg bad144 on st506, they too can be recovered & examined, usually only a small burst of data is unwriteable, the sector spared out, the rest of the data is still clearly readable. I've personaly done this. Those supposedly unusable sectors are invisible to normal users on IDE & SATA, but I'm pretty sure I could read them if I tried hard ... I am a computer consultant smiley icon
      • I have done data recovery. I also wrote a public free source tool valid, it does excellent byte recovery from defective floppy disks, regardless of OS. It actually runs better on MS DOS than Unix! Though I don't currently have a .exe for DOS on line. I also wrote a public free source tool slice, it does sector recovery from defective tapes (or files on disk) I don't currently have a .exe for DOS on line.
      • PS: A friend Geoff used to cook his CDROMs in his microwave oven, it nicely crazed them, I don't recall getting an answer from him, if he used a glass of water as well as dummy load to avoid over stressing the Klystron; He was an electronics engineer though.

      PS: External media

      If you keep your personal data on an external USB disk or stick, then if you need to have a service technician repair your PC, then the tech. & all his company colleagues won't have access to your data while the PC is away. However it will be physically easier to steal whole drive. & Remember USB sticks are very light, much lighter than the shiney plastic wrapped cereal bar I caught a black & white bird (Jay ?) hopping out of my living room with (fortunately too heavy to fly with that cereal bar, but it would have easily managed a shiney USB stick.

      Keep your USB stick on a heavy key ring. & If it travels on your car key ring, leave most of stick encrypted, just a Read-me file on top with a friends address in same town, but Not your address inviting thieves to visit with your front door key ;-)

      PS Smart Phones

      Some of the above considerations apply to smart phones too.

      PS Inadvertent Export To Web

      If you have inadvertently published data on web, do not simply delete it! (Because it may have been picked up by public archives such as Way Back machine & others, which periodically update to copy your latest version). (This author's page have been archive copied by several other sites without ever a contact to me, (& annoyingly some of those spider/mirrored copies have been many years out of date)). So Instead replace your private data with de-fanged deliberately obfuscated/ changed/ corrupted data in same place, (& maybe of about the same size ?).
  • Physically Scrap Device Yourself

    (For those who have local computer specialist friends like me: Old tech you could give me or another computer specialist & I or they could delete your data then use or scrap hardware.
    (One reason specialists can use your old hardware, is that Free Software is more efficient & flexible, & less demanding of ever new hardware than Microsoft.)

    How To Scrap Your PC:

    • Unscrew disk drives out of PC
    • Cut thin wires between disc circuit board & disc
    • Wear goggles
    • Place disc on concrete & smash disc drive in with sledge hammer
    • Use a fat nail (maybe a stiff masonry nail0 & hammer to make a small dent on disc drive, half way between centre spindle/ rotor/ bearing and end of drive away from power & data connectors, (cos the connectors end has more internal steel & magnets to obstruct drill) then use the pilot dent to centre an electric drill through drive chassis & maybe through disc (some discs are glass) , one could put a nail through disc chassis hole & smash or drill the disc,
    • Dump metals in metal scrap bins at dump (more choice of bins for different scrap at the local dump, not at local street tin can collection receptacle.
    Above is good enough for general public, but ...
    • There's small quantities of gold in a PC etc, one can do better:
    • I fully strip old PCs etc, separate ferrous = magnetic = steel bits from aluminium bits.
    • separate out copper containing cables,
    • separate PCBs (printed circuit boards with copper & gold (I leave them in the elektro container at the tip, the one with TVs PCs, Stereos etc)
    • My Munich tip has lots of different containers
    • Tunbridge Wells has quite a few too, certainly for ferrous, non ferrous, & other electro stuff.
    • I wouldn't dream of paying or trusting an outside company at their choice not mine to either delete my data off my drives or sell my drives & devices on at their discretion.
    • Companies I know of, if they clear out old devices, & if they don't trust employees to be skilled to erase all data, then they pay scrapping companies that guarantee destruction & do Not no sell on or donate to 3rd parties.
    • Its nice to think of hardware being re-used, but not going to extent of committing to pay unlisted fees to a company to take away one's data with hardware that can access it.
    • For a company getting rid of hardware, it may be safer to pay a freelance on site to erase data under eyes of owner/ manager, then let owner or specialist select a known school, charity etc to receive old hardware.

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