Are Deleted Data Files Ever Truly Deleted

Deleted Data Files

So, are deleted data files ever deleted from your computer? The deleted data may be gone, but it’s not forgotten.

Personal computers have become disposable commodities (Ahem. I mean a recyclable commodity).  In the early days of personal computing, when PCs were much more expensive, people tended to hold on to them longer.  Some of that was cost, but a lot of it was that the technology didn’t change as fast as it does today.

I was thinking the other day about how many personal computers I have owned over the years.  Being an uber-nerd, I know that I’ve had much more than the average consumer (it’s in the double-digits).  Some were bought, and many were donations from friends who no longer wanted them (as they had purchased newer machines).  A few were throw-a-ways from institutions and companies that I had worked for that were disposing of perfectly good machines.  There was nothing wrong with any of these computers other than they weren’t the ‘latest and greatest.’

MACs, PC, Workstations, and Laptops

Some were Macs, most were PCs, many were workstations, and a few were laptops.  I’ve owned one or two servers and even had a SPARC workstation at one point.  What did this menagerie of machines all have in common?  ALL of them had recoverable data on their hard drives. Old Computer Deleted Data Files

Most of these devices had fully functioning operating systems that booted right up.  A few were password protected, (easy to get around – and that’s for a future blog entry) but most were not.  Most had their files deleted (e.g. deleted files from Documents and Downloads folders and then emptied the trash).  Only a handful had their hard-drives wiped.  Many of the wiped drives were only reformatted via the operating system.

Deleted files and formatted hard drives do not prevent someone from recovering data.  Thankfully, these machines all ended up in the hands of a ‘white-hat’ good-guy nerd like myself who can tell you how to protect your data (and yourself) from the bad-guys.

Do We Need To Be Reminded About Password Security

When deleted data isn’t deleted.

We delete files every day.  We throw documents, spreadsheets and photos in the trash/recycle bin, and occasionally we empty the trash.  Files are gone, right?

When you save a file – the computer writes data to a hard drive and places it on a section of the disk.  When you delete that file, the operating system says that space the file currently occupies ‘is available’ if you want to write something new to it, but it does not remove the file.

Think of it this way.  You have a bookshelf (hard drive), and you place a book in it (save a file to it).  Then later you decide you don’t want that book.  Instead of throwing it out (Uh. I mean donate to a public library) you leave it there until you add another book to the shelf.  Even then – there might be room for your new book without having to remove the old one.  That book (file) still marked for deletion, is still there intact.  If it’s there – then someone (including you) can get to it.

And that’s not all.  When you reformat a drive, you are doing the same thing as deletion, but on a larger scale.  To use the bookshelf analogy – you are now saying the entire bookcase is available for use, but you haven’t removed any of the books.  You have merely thrown a tarp over them.

So, what can you do to protect yourself?  What utilities are available to clear the bookshelf?  Come back for part two of this series, and I will share some of my favorite data deletion tools.

About the Author:

John Castrege is the Security Systems Administrator for Campus Safety at Haverford College & Bryn Mawr Colleges. He holds a Bachelor of Science in Criminal Justice from York College of Pennsylvania and a Masters of Software Engineering from Penn State University.