Hello, data-tamers!
I have some kitchen work happening right now to address the aftermath of a long-unnoticed dishwasher leak, so I'm banished to the basement until some mold-killing spray dissipates. What better time to talk about making sure you know how to thoroughly delete some of your data?
...although, upon further examination, these topics have nothing to do with each other. Hmm. 🤔
First, let's see how I did this week with my 2025 consistency challenge project (collecting and cleaning multiple decades of archives from 20+ hard drives):
- Week: Q1/2025, Week 4
- Files deleted: 61,669 (24.2 GB)
- Files triaged: 2,215,973
Not too bad! Definitely better than the big fat zero I got last week. The "deleted" vs. "triaged" numbers are so lopsided for two reasons: first, I worked through many folders that I'd already cleaned a bit many months ago. Or years ago, more likely. There wasn't much I could get rid of without digging deeper, but this stage of the process isn't about digging deeper. The second reason is that this included a nearly complete backup copy of my entire "user" folder that I work from daily, which is...a lot of files. Most of them will disappear once I get to the deduplication step.
To recap, remember that I'm working through the "data triage" process, which looks like this at a high level:
- Gather all of your data into one place (by copying, not moving, so you have the originals as a backup)
- Delete as much easy stuff as you can manage up front (operating system files, program files, etc.)
- Deduplicate the entire dataset with an app like Duplicate Cleaner Pro
I'm now mostly through the second step. The third step completes the data triage process, at which point it will be time to do that deep dive I mentioned a moment ago. That will likely take the rest of February and March--perhaps longer.
If any of you need to go through a similar process but aren't sure how, let me know and I'll be happy to get you started.
Lazy Deletion
After last week's email about sorting through the data on a couple of my dad's old hard drives during a PC upgrade, I held off describing the last step of the process: wiping the old drives so they could be sold or donated.
Many of you are (rightly!) concerned with what happens to your old data, whether it's just a vague unease about someone else seeing your old school assignments, something more personal like pictures of your kids, or something that would allow identity theft like old tax returns. Even if you know how to collect and back up your data, what about the clean-up process? How can you be sure it's really, truly, unrecoverably gone?
You've probably heard that even when you delete something, it's not really gone, and some nefarious hacker can get it back if they only try hard enough. While it's true that undeleting with a tool like Recuva or Disk Drill is possible in some cases, it's important to understand when and why that's true--because it isn't true all the time, even when you make no particular effort to delete something.
On magnetic media--which includes tape drives, floppy disks, and mechanical hard disks--writing data to media is a technically expensive operation. It takes more time and energy to write data than to do just about anything else. Because of this, filesystems were designed to allow the "delete" operation to take a shortcut: it simply marks the space as being available to write again, without actually overwriting the whole space with anything else.
Unless you're concerned with actually erasing the data, this is a great feature. Not only is it much faster, it also means you have a reasonable opportunity to undo mistakes (something I've taken advantage of dozens of times over the years). In these "mark-as-empty-but-don't-really-erase" situations, eventually the filesystem will write new data from new files over the old space, at which point your original data is actually gone.
However, on non-volatile media--which includes modern solid-state drives (SSDs) in either 2.5" or M.2 NVMe form factors--this is generally not the case. Fully erasing areas marked as "deleted" generally occurs much faster, sometimes right away. The firmware on the drive takes care of wiping empty areas on a regular basis as part of a process called wear-leveling (which prolongs the life if the drive). Further, the firmware on the drive typically won't provide access to data that's been erased, even if it's still physically present.
As a result, undeleting files from modern SSDs is typically far less likely to work. It's not impossible under exactly the right circumstances, but the odds are much worse than doing so with magnetic media. This also means your data is automatically less likely to fall into the wrong hands if you deleted it from a modern drive. But how do we make sure?
Secure Deletion
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Let's say you have a drive full of photos of your kids and old tax returns. You've backed everything up into a new safe place, and now you want to decommission the drive so you can donate or sell it.
Now comes the time to wipe it clean, and fortunately this is not hard! If you're a Windows user, I recommend CCleaner, an app that's free for home use and fills this need quite well using a built-in tool called Drive Wiper.
Drive Wiper gives you the option not only to wipe just the free space on a drive (the areas you've already deleted), but also the entire drive regardless of what's on it now. You can also choose whether to a a simple 1-pass overwrite or something more thorough with additional repetitions.
Piriform provides a couple of relevant guides:
If you're more technical and want something with a few more options for the overwrite mechanism, you might also try Eraser from Heidi.ie. This is also free, and also Windows-only, but very powerful and straightforward to use.
On a Mac, the operating system's built in Disk Utility provides the option to securely erase removable drives. Also, modern Mac systems have hardware-level encryption mechanisms such that your old data is thoroughly wiped if you reset the system to factory defaults (again, done through built-in system tools).
...and if you use Linux, there's a good chance you already know how to do what I'm talking about here, or could figure it out in a matter of minutes. If not, please ask!
Finally: if you don't need to pass the drives along to anyone else, there's always the physical method: sledgehammer, rifle, or industrial-grade hardware shredder. These are all perfectly acceptable--and even preferable to some degree--if your only goal is security and privacy.
In the case of my Dad's drives, I actually used Heidi.ie's Eraser tool for the mechanical drives and CCleaner for the single SSD (main boot drive), although in retrospect I could have just used CCleaner for everything. I'm confident that none of his old data will ever fall into the wrong hands because of those drives.
If you'd like some pointers to accomplish something similar with your data, let me know, and I'll be happy to help.
Until next time: happy data-taming!