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I used to have a IBM Thinkpad (Lenovo) T440. I have been using that laptop for over 8 years.

This device has been reset to factory default multiple times (probably up to 6-10 times if not more)

Every time when I selected to reset the system, I chose the “Remove All Data / Do Not Save Any Data”. The way I used to reset was by following the step of Thinkpad’s Own Recovery System which could help you to reinstall WindowsZ

That laptop’s Screen was broken and I had to gave it to the computer repair shop to let them dispose it for me.

My question is this, I didn’t have the chance to wipe clean the data myself before I was ready to dispose it.

I am a bit regret now that I gave my trust to that computer repair shop to sort out the rest.

Bottom line is I don’t have critical files or personal data in that laptop after the last reset I made.

I am just wondering would any people be able to retract my data before my last reset or even up to the point when my very first test was made.

I know you’ll have to rewrite the hard drive multiple times over and over to completely erase the very old data.

My multiple resets were all happened when my system got so slow and even infected my virus or something. So I assume my hard drive had been already overloaded multiple tomes my tons of new data over the old data, not to mention full clean resets multiple times as well.

Am I worrying too much that my oldest data would still be retractable by hackers or there is a mere chance they could only probably retract data up to the point when my latest reset was made?

Looking forward to your answers!

  • I don’t personally know enough about file systems to be able to answer this intelligently for you, but I did want to say the way you phrased your question was really friendly and made me happy to read. Thanks! :) – securityOrange May 16 at 5:38
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First of all, most computer repair places are not fully equiped forensics labs; so, they will probably only be able to see what you've saved since your last reset.

Now, if your computer repair guy is actually a data forensics expert moonlighting as a repair guy, it's a different story. When you delete data from a computer, all the data stays there but the blocks get marked as deleted; so, a factory reset will generally hide your data without destroying it. Then as you write new data over the old data, the blocks often only fill up partially leaving fragments of data in what is called the slack space. There are many tools that can be used to scan slack space for deleted files, but the older a file is and the more often you write to or defrag your disk, the more likely you are to see that data overwritten. Some tools are designed to make assumptions about previous states of bits based on residual charges meaning that the past few over-rights can be sort-of read, but not with 100% accuracy.

So to answer your question, there may be data left over from one or many of your previous resets for a really smart and unethical person to find, but the older the data is, the less like it is to be recoverable. That said, having worked with enough IT people in the past, most professional repair places will drill or shatter your drives as a professional courtesy before disposing of it because they expect their clients not to know to do this. Or, if they choose to refurbish a drive, they will do a multi-pass rewrite to protect your privacy, and their reputation.

As a final disclaimer: technically data can still be pulled from a shattered drive with very expensive forensics equipment, but unless you think you are high up on government watch list, that is not a very realistic concern. But, if you think tin-foil hats are a reasonable security precaution, and you really want to make sure your data is unrecoverable, the only way to truly do that is to melt your hard drive... but that is supper bad for the environment and your health.

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    Another option aside from power tools and slag pits is a hard drive degaussers ... this is how most government agencies deal with stuff that is above non-class. Its basically a very very powerful EM device that will also make most of the lights in your building flicker when used. – CaffeineAddiction May 16 at 17:57
  • That is incredibly amazing insight! About the slack space you talked about. – Extrasecurity May 22 at 23:35
  • Basically my most worried reset was back in 2008 when I saved some ID scan copies in there. After that, I had probably up to 5-8 if not more hard resets happened whenever my laptop’s memory is full or even crash due to overload. So would identity thief still be able read those ID traces through the slack space you described? Also, my another laptop was also disposed not long ago but I used professional Eraser tool to destroy data at least 3 times repeatly, would this have been a safeguard of my data possibly? Thanks! – Extrasecurity May 23 at 0:07
  • I would not be too worried about data that old being recovered, especially if you repeatedly filled the hard-drive since then. There may still be fragments of those IDs in there, but probably nothing usable. Eraser tools vary, but any half good one should do a bit-by-bit wipe of the drive which deletes the slack space as well. 1 pass on a modern hard-drive or 3 passes on much older ones will prevent anyone without government sponsorship from getting anything since you'd need a specially modified electron microscope to read data past that point. – Nosajimiki May 23 at 0:40
  • Also, if you want to remove slack files on a drive you are not wiping: pcworld.com/article/2464163/… – Nosajimiki May 23 at 0:42
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If you don't trust them or know that the repair shop uses the proper tools I'd just pull or ask them to pull your hard drive. If you don't want the drive then you can use a power drill to drill holes through the platters a bunch of times BUT with enough resources some data could possible still be recovered which is why some recyclers actually put them through a chipping machine and it gets mixed together with other drives so good lock reassembling out of a pile of drives in partial powder and chips.

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