How to Permanently Delete Files

he's not exactly working at all Thrusters. We still haven't started receiving mail about where I get these quotes from, so I'm curious to hear once those started coming in. Actually I'm sure I'll be buried under an avalanche. But that leads me to a little actual listener mail. This mail comes from Griffin. So, first of all, Griffin, you have a really cool name, and here is the mail. Hi, I just wanted to send you a note about deleting

files on a computer. Your recent data recovery podcasts correctly mentioned that when you delete a file or empty the trash on your computer, it really just deletes the pointers and the data is still there. Sometimes. However, both Mac os ten and Windows XP have newer and newer versions have easy to use secure erase features. If you turn these on or run a secure a race free space feature, it will actually overwrite the deleted files space with zeros.

Your os can't find it anymore no matter what. Even so, the U. S. Department of Defense prescribes that this be done seven times before it is considered safe, and even then there are higher specifications for safe deleting without destroying the physical media. There are also software available that can cause physical damage to a drive and its platters using things like vibrations caused by repeated looping instructions. Software can make a drive head shatter or heat up the drive platter.

Fun huh. Anyway, just wanted to share some additional knowledge with you. Hope your summer is as great as mine. Well, thanks a lot, Griffin. We're actually going to do a podcast about permanently delete being files because we had several people ask us about that after we did our data

recovery podcast and you've kind of covered some of the basics. Uh. Yes, when you delete a file, what you're really doing is deleting a pointer to that data, right, Because if you just drag a file to your recycled band or trash can and tell it to delete it. It, you know, gets it off of your hard drive, and and basically when it removes the pointers, it's making that space available

to be written over again. But typically if if all you're doing is just deleting it under the normal circumstances, Um, I will explain why I say that. In a moment. Um, all you're doing is saying, yes, you can go ahead and take these two megabytes or whatever, and next time you need space, feel free to go ahead and write over this, because I don't need that anymore. But it

does not actually remove the file completely from your hard drive. Right. So, in other words, if you delete something, then it may be possible to retrieve it using data retrieval software. Delete software essentially is what it's usually referred to as, which is really useful. If you go, oh, no, I can't believe I just deleted that. Yeah, I can't believe it. Sometime my term paper. I mean I've accidently deleted articles. I've done that. Yes, I've accidentally deleted articles when I

got angry. Um no, that's a joke. Please don't send anyone to me. Uh the Yeah, So, if you delete something by accident, there are ways to retrieve it, assuming you haven't, you know, downloaded new information and had that that those old files overwritten by your computer. Uh. And if you remember our podcast about hard drives and how hard drives save information to the physical media, you'll remember

they don't necessarily do it sequentially. Actually, platter based ones don't do it sequentially at all, at least not in most file systems. Right. Yeah, we did mention that older DOS versions do, like the ones that were used by NASA, do save it sequentially. But in your average hard drive system, your data is being saved willingly in a way that kind of sort of makes sense, but it's not necessarily sequential. So when you over when you're saving you data, there's

no guarantee that you're actually overwriting old files. You may be saving that too unoccupied space on your hard drive. So uh, it may even be that something that you deleted months ago is still sitting on your computer. That's true, And this is important because whereas a few weeks ago we were talking about how you can save files that have been seemingly deleted from your computer, let's say you actually want to make sure that something is gone for good.

For example, you're selling your computer to someone else, or or donating it to to a charity, for example, for an older machine, and you think, wow, you know all those tax files I had on here, I'll just lead them. Well, if you just to lead them, they're not gonna be really gone. And it is possible that someone who is enterprising enough can go in and get very sensitive information such as here in the United States, your social security number or something else that could be used to steal

your identity. So let's say that let's say that you're the I T head of a government office. Now, the information that's on the computers in your department may be extremely sensitive. In fact, some may be uh related to to national security. And so it's of utmost importance that you make sure that that data is completely destroyed when you are going to get rid of an old machine. Um. And so it becomes really important to know what's the

process for deleting these files. Uh. So you wanna you want to get rid of something, you want to overwrite that data. You don't want to just um, just assume that when you delete something that's gone, how do you overwrite a file a specific file, Well, it depends on the computer system that you're using. This is true. UM, you know that what we were talking about earlier. Yes, the U for example, the Macintosh operating system with which I'm probably a little bit more familiar than Windows UM,

although I've used Windows for many years now. UM actually has an option UM in the in the file menu when you're looking at the at the trash to you have the option of a racing or emptying your trash or secure empty trash, which is basically not only does it UM delete the files on those sectors on the hard drive, but it also overwrites them with ones and zeros multiple times in order to you know, obliterate those files.

So it's it's going ahead and writing information, uh, you know, basically gibberish information to those sectors in an attempt to completely get rid of it. You can, and you can, as we were mentioning before, to do that in other operating systems. Yeah, in Linux, if you're if you're using Lenox, most distroys of Lenox have a shred command, and so your shred command shredding is it's essentially what it sounds like when you're you're physically shredding a document. The ideas

that it's shredding the digital version. And again what it does is it it not only deletes the information from your hard drive, but overwrites it for you. And you can even adjust the number of times it it passes that information and overwrites it using various command line functions, so you could just overwrite at once, or you could set that overwrite number to a much higher number like seven or seven times. Is the Department of Defenses UH

basic rule of thumb which Griffin mentioned. Um, there's also another approach called the Gutman method, Yes, which Gutman is UH. It's well, it's it's named after a technology expert who came up with thirty five different ways to overwrite UH data. Since then, it's his method has been kind of misinterpreted to mean that you need to overwrite data thirty five times to really obliterate it. That's kind of a misconception.

That's not really what Gutman was saying, And in fact, Gutman u in Peter Gutman, I should say, it was a paper called Secure Deletion of Data from Magnetic and Solid state Memory that was the thing that kind of gave birth to this whole thirty five passes to truly erase the data so that you don't have to worry about data recovery specialists getting hold of it. Um that he He later wrote an addendum to that, an epilogue to the paper, which essentially said that two passes of

random data should be enough to obliterate information. Uh. Some people suggest more because of the fear that future data recovery strategies will be able to get past that. There's also the possibility some people think that there may be a stability that because because it's a magnetic storage um uh media the classic hard drives at any rate, it's possible that empty sectors could have their bits aligned magnetically

with other sectors. So even if you've overwritten one thing, there may be a trace ghost element of that old data on an empty sector, which theoretically you could detect if you had an electron telescope. Yeah that that kind of detection requires a certain amount of funding and expertise and patients. Um. The average consumer does probably does not need to worry about someone going after his or her computer with an electron microscope. It's just not gonna happen.

And uh And some experts will tell you now, among them Craig Wright Dave Kleiman and Shyam Sundar that overwriting hard drive really you only need to do it once and that is enough because it will obliterate whatever the file was and and it won't. And while people have said that there are data recovery ways of getting past that, they say that the way that we store information magnetically, Now, uh, that's not really the case. That this whole seven pass

this thing and thirty five pass this thing. These are all based on misconceptions and are really overkill. That being said, it really doesn't hurt you to over to overwrite multiple times. Another another method that people, some people have been using, and I don't know if you encountered this in your research or not, Jonathan, encrypted e racing. Yes, actually I

saw a cool one called secure delete. This was a program which actually encrypts your file before you delete it and overwrite it, so that should someone have the ability to recover that data, they're going to recover an encrypted file. And encryption, if you are not familiar, basically is a

way of encoding the file. UM. If they wanted to try to open it, they would be asked for a pass key UM and it could be something I mean really obnoxious or I don't even know if do you know if secure delete um actually tells the user what the code is, so it's encrypted with a key that no one knows. Yeah, it's like it's like you've been given a coded message but no key to to decode it.

So that's I mean, that's the whole point. That's what makes it secure is if it if it did somehow provide you that key, then you would be able to decode the message and get back to the original file structure. But by keeping the key a secret, then it's out

of an extra level of security. Now, so so you would have to be able to one retrieve the overwritten file, which is then encrypted, and then to break the encryption to get to the original file, which is I mean that's this is like like major secret service kind of stuff that that confounds really really smart people as opposed to people like me. I'm just I'm just smart. I'm not really really smart because I use terms like really really smart. Um. All right, then, well, um, but those

are for individual files. Should we talk about ways to uh if you want to just go ahead and wipe the entire drive clean? Yeah, because if this is a good using these these methods are are good for Oh and yeah, we didn't really mention it, but yeah, Windows has it has their own They have their own their own programs as well, and some of those are like

Griffins that are incorporated into the OS. But they are also products that you can purchase that will allow you to do this kind of thing, like BC wipe allows you to delete an overwrite individual files. Blanco file shredder lets you do that. It also lets you do folders, so you don't have to do it file by file. You can do an entire folder you want to um and then there are there are a few others. There's a race your hard Drive dot com which uses the

d D method of racing doing seven passes. Department of Defense. Yes, thank you, Department of Defense. I'm we're on really good terms, so I just call him d D sometimes Dodd anyway. So yeah, there are also solutions for PCs. Now, if you don't if what you want to do is wipe the entire drive, because what you're doing is like what was saying, you want to get rid of your computer or perhaps you want to repurpose it or whatever, and you don't want whatever was on that computer to ever

fall into someone else's hands. Um, yeah, you can, you can. Actually, there's several different methods of wiping everything off your hard drive and overwriting it so that, um, so that nothing remains. And some of those are again, uh, commercial products like killed disk is one. You can purchase killed disk and what it'll will do is it'll it'll erase and overwrite the dear hard drive, um multiple times, I think. And there are other products that do the same sort of thing.

This is again what what the Department of Defense does if they're ever going to get rid of a machine. Now. Um, when we were talking earlier about Griffin's email about secure a race, that actually is uh not really platform specific. That's actually something that the hard drive manufacturers have been including in the firmware for the drives for a while now.

And basically that means that there is some some information in the in the hard drive itself that if you know how to tap into that information, the drive will go ahead and delete everything on there securely. Um. The trick is they don't want to make that something that you can do easily by accident. Yeah, obviously that would be a bad thing. And this is a good time to actually mention that if you do ever need to wipe your hard drive um again, make a backup of

your drive first. Uh. This kind of sounds like it's ridiculous and that you don't want to do that. But let's say that you've deleted the stuff that you don't want on your drive at all, um, and whether or not that those deletions have been overwritten or whatever, that

that's kind of beside the point. If you if you make a backup of your hard drive, and then you are manually choosing which which bits of information, which files and programs you want to bring back onto your new device or either you're repurposed computer perhaps um, then you can avoid pulling over the stuff that you didn't want on there in the first place. But making a backup is important because once you wipe that, it wipes. Wiping

a hard drive wipes everything. It's not just your documents or your files, it's also all your programs and even your operating system. So you'll in order to make your computer useful again, you will have to load in either copies of your old OS or a new OS. If you want to change your machines purpose, if you want to switch from a PC to a Linux based machine

for example. UM So, yeah, you gotta keep that in mind too, that when you do these wipes, it's going to wipe everything, which is a good thing, as it turns out, if you want to really erase all traces of you know whatever, like again, if it's financial records or uh, corporate intellectual property, that kind of stuff, it's

necessary to do that. Yes, secure race going back to that now with the work of Dr Gordon Hughes and a group called the Center from Magnetic Recording Research at the University of California at San Diego and UM actually secure race is uh so thorough that the National Security Agency and National Institute for Standards and Testing are behind

using secure or a a race. Unfortunately, according to UM an article that I read by Robin Harris at ZD net, uh the n s A stopped supporting Dr hughes Is research. But you can still use um the secure race functionality of your machine. Now, if you're a conspiracy theorist, you say, hey, they're supporting this because it doesn't work and they want to be able to get to my data. I'm not a conspiracy theorist, No, of course, I don't know how you would have thought of that otherwise, But I just

thought it was funny. I thought that heaving off the email like of course, that they're recommending you use this because that way they can they know the secret and they can get your data. First of all, they're way too many of us out there with computers. They can't be after all of us. It's just too time consuming. I mean, they don't even have the money or the man power to do that. So we just discount that immediately. Jonathan, Well, yeah, yeah,

I'm sorry to use some critical thinking. It's I know it's so irritating. Um um, go ahead, I apologize. No, No No, we were us starting at the same time. If you want to wipe your entire drive clean for whatever reason, uh, you can't really be logged into your machine when you do it. You're gonna have to boot off of a CD.

There's just no way around it, because well, yeah, you've got to boot off some kind of external drive source because if you are running your own computer at the time, it's gonna go put wait, I can't delete this because it's running right now. So you're gonna have to to to use some other form of disk and uh log into your machine, or you know, start your machine so that runs off the CD or the flash drive or

an external driver. However you're doing it, a secondary drive in the machine probably would work, um if you do it right. And uh, that way you can actually run some of the utilities that we've been talking about, UM, either a block or racing program or secure a race or something else. UM. And that way you can actually

you know, go ahead and write over those files, all right, Chris. Yes, Let's say that you're super secret agent and you're deep undercover and your cover has been blown and you know that they're after you, and you know that your computer is going to be seized. Odd. Sorry, I won't live to see tomorrow. Right, Okay, see, great agent man, they've given you a number and taken away your name. So number seven, you've you're deep undercover and they are out

to get you. Number seven, number one is on your case. And so you want to get rid of all your data. You've overwritten your hard drive, but you want to take that one extra step. What can you do to absolutely guarantee there is no way they're going to get any data off that computer? Are you serious? I'm serious? Like you have overwritten it and so you've done everything electronically that you can do to get rid of the data, which is that's the next step, and that's important. That's

a good first step. Yeah, if you're absolutely in, if you're pretty sure that nobody's going to get hold of this drive and try to pull the data from it, Uh, then you can use these electronic methods. But if you really really want to do this, if I'm trying to protect what's left of my what the remaining shreds of my secret agent work, um, I am going to remove keeping with the secret agent motif here, I'm going to remove the drive from the computer and shoot it with

my Walter Walter PPK. Okay, so you're so you're I'm a secret agent, you're now a British secret agent. You know you didn't pick number seven and I had to fix my Walter. Okay, but you don't really need to shoot it. You're not gonna use your baretta. You can pull that. You can pull the hard you can pull the drive apart and take the platters and drill holes in the platters or scratch them up with something scratchy, or use an industrial shredder that or work. There are

actual industrial shudders out there. Does line specifically to destroy media like DVDs, CDs and hard drive platters. Yes, and so all the stuff that we were telling you not to do, and the hard drive podcast dot data with every podcast. You can do that all you want. If you're trying to drop it, smash it, step on it, you know, grind it up. So the idea, Yeah, if you grind it up, you've pretty much guaranteed that there's not gonna be any no one's gonna get any debt

off that thing. Suppose of it in one trash, can't part of it in one trash, can go downtown and get rid of the rest of it. Your credit cards and uh, you know all those pictures of all those those film fatals that you met up with a long while on your undercover spy Adventures on our spy Facebook profile. Yeah, I can't even say their names because they're way too suggestive. Okay, then well, yeah, you look at the James Bond names of the women, and there are terrible, terrible shame on you,

James Bond, shame on you, um at any rate. Yes, yeah, that is the ultimate step is if if in fact you need to destroy the physical media because of some reason, you know that there is some someone's out to get your data and you just want to make sure it's gone. Yeah, first, electronically override everything. Always do that first. Then you can

look at your various ways of destroying it. And I've seen lots of different ones, like I like we mentioned before, I saw one that was an industrial sized drill press that would drill an enormous hole through an entire hard drive box. Or you can like disassemble the box, take the platters out and destroy them. Or if it's if it's a solid state, then you just take a hammer to it, just just smash it into tiny little pieces.

It's good to be a gangster. Yeah, I'm sorry that I heard it was hard to be a gangster, um, but yeah, it's um. It's something that you're you you can actually do physically to to destroy the drive. And as we were talking about again, you know, they recovered a hard drive, They recovered information from a hard drive

that had been recovered after the Space Shuttle crash. So you know, anything that you can do to eliminate this data from the drive, you want to do and that oh we know what we didn't touch on something in betweens. Oh yeah, um, you know degaussing, and this is a tech. This is has to do with a famous German mathematician named Carl Friedrich gauss Um. He did a lot of work with mathematics, but also was very interested in the

Earth's magnetic field. In fact, he invented the magnetometer. But a gauss is a unit of magnetic uh um, I'm sorry, I can't read magnetic conduction. See, this is what happens when I go back to paper. I can't read my own writing because I type all the time. Now. One gauss is the magnetic flux density required to create an electromegna motive force of an advolt in a centimeter of anyway. Yeah,

and so a unit of magnetic measurement. And basically when you degauss to drive, you're running magnets over it to try to change to try to eliminate the data by manipulating the magnetic field on the platters because of course hard drives are or the typical platter hard drive anyway is a magnetic storage medium. Yeah. Actually, um, and I

wanted to bring this up because it's funny. The day we're recording this, uh, I actually saw a message on Twitter about someone who is going to do an experiment or wants to do an experiment with magnets and hard drives. And uh it's Patrick Norton, who's with Revision three. Um honestly of of many other shows before that as well. Yes, he used to be with tech TV. Uh and uh, yeah, Patrick Norton, whom I've met once, so Hi Patrick, Um.

Patrick Norton is looking to be able to use a really powerful natural magnet to see if it can if he can wipe hard drive live on tech Zilla. Okay, of course there's a Revision three show now at the time of this recording that hasn't happened yet. I'm sure by the time this podcast comes out, Uh, they will

have have shot that and uploaded it. So if if you guys want to see some of something like this happen in uh an actual life, you can go over to Revision three and look at Texilla and try and see if you can find the episode where Patrick Norton wipes out a hard drive with a really powerful magnet. Okay, that's that's pretty cool. Actually, what's happening today? Yeah? Today? Um, And just so you guys know, We don't normally talk about the day that we record the podcast, but this

is Wednesday, August twenty. Yes, just to give you guys a kind of a reference point if you want to look up that taxilla thing. Yeah, so yeah, I can. I can attest to, uh, what will happen if you hold a twelve pound donut magnet up to a television screen, and my parents, we'll also attest to uh me being grounded. So if you hold up a donut magnet to the television screen, Chris will be round it. Yes, exactly. Uh no,

don't do it, Just don't do it, please. I just you know, I'm thirty nine years old and just got free. Um and that happened I was in junior high school. Wow. Uh No. But honestly, if you use a powerful magnet and put it right up to the hard drive that you have removed from your machine, it's going to do a lot to uh realign the magnetic field and structure

of the information on those media's. Yeah. We actually talked about that in the sun Spot podcast about how if you if you do have a really powerful magnet and you put it near a less powerful magnet, the less powerful magnets magnetic field will realign to the more powerful magnetic magnets magnetic field. So yeah, it's just one of those neat things about magnets and uh yeah, so those are not good for anything that uses magnetism as its

storage method, that is correct. So so yeah, that's another good point, um, both in if you want to try and get rid of data or if you want to prevent that from happening. Uh yeah, it depends on whether or not you know you have bagnots nearby and handy. Um. So yeah, that kind of wraps up the discussion about permanently deleting files off your computer. Oh I have one other thing I should mention. Oh and I do too. Okay, do you want to go first or shall I? UM?

I was just gonna say, if you are going to go so far as to take a sledgehammer to your hard drive or a power drill or something else to it, please take safety safety precautions because you do not want to lodge a piece of hard drive in your eye um or or worse. I mean, you could seriously get hurt because once that thing busts open, it's there's gonna be lots of little shards of hard drive everywhere and

you don't want to get hurt. So please there, please take safety precautions and where eye protection if you're going to do something like that, right, and and remember that there are toxic elements within computers as well, definitely, so lead and mercury and all sorts of other stuff. Yeah, so you need time you're you're messing around with stuff

like that. We treated it pretty lightly, but yes, there are there are actual possible harmful things that could happen, So keep that in mind whenever you're doing anything with computers. But the thing I wanted to mention was that we've really focused on computers in this podcast, but this really holds true for other devices as well, because we have more and more devices now that have these kind of

elements to them, like smartphones. Um, and so for smartphones, you'll have to look for specific kinds of applications or you'll have to find a way of getting into the roots system of the smartphone in order to really wipe it clean. But that is a big thing. I mean, you don't you don't want to if you're getting rid of your phone, you want to wipe that phone before

you donated or get rid of it. Because it's going to have all those contacts and things like that, especially if it's safe to the phone and not to say a simcard, And the same holds true for things like game consoles. The reason I bring that up is I got an Xbox three sixty and my my wife purchased it for me as a present, and she she bought a refurbished one, which is fine. I had no problem

with that. The thing I did notice was that the previous owner had neglected to wipe his information off the Xbox three sixty, so his Xbox Live account information was still active. Now, if I were a dishonest, terrible person, I might try to use that information to log onto Xbox Live without paying for it to see if perhaps it was still an active account, and that would have been really dishonest and I'd be stealing essentially. Now I'm an honest person, so I went through the trouble of

actually wiping that off myself. But even then I just did the simple delete because you know, I wasn't gonna I didn't worry about overwriting it. It's not my information, so I just deleted it the normal way. If you want to delete something permanently off Xbox three sixty. That's another podcast. So anyway, just keep that stuff in mind. Remember that when you hit that delete key, it does not necessarily go away forever. So if you're trying to

really delete something, take the proper ups. Be careful because you don't want to delete everything necessarily. Well, I mean, unless you really do, which case have at it. But otherwise otherwise, be careful because you don't want to end up making your computer into, you know, just a basic electronic calculator that you're gonna have to load everything back

onto again. Uh and UH. If you have any questions or concerns, you've got any criticism, criticisms like the way I say criticism, or you have suggestions for other topics,

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