[Jon1001]

Accidentally stumbled across this site a while ago about why secure deletion is important. It explains it very well and if you are thinking of selling an old PC, it may be a good idea to 'shred' the hard drive as described here. Just one question. Does anyone know why you need to do multiple passes to get rid of data?

[biagrin]

multiple passes would be needed because if you delete a file it still remains on the disk. When you add a new file the drive doesnt go out its way to deliberately overwrite the deleted file with a new one.

I suppose if you were to open ms paint and quickly draw a black line across the screen and then change the color to green and do the same thing again, trying to overwrite the black line, then it would be a similar principle to what the HDD is doing with the files.

[valis]

multiple passes, or 'zero fills', fill every cluster on the hard drive with data, essentially rendering the drive useless. When you delete a folder/file, all you are doing is erasing it's record in the file table, not erasing the data. You just tell the os that that spot on the HD is no longer occupied, feel free to use it. If the OS uses it, great. If not, the data is still there, and it's not that tricky to get back.

If you use an app like DBAN, it's virtually impossible to get data back from the hd. That's the app we use to wipe machines before we donate them. It's just shy of physically shredding the drive, think it's DOD-M compliant, but I could be wrong on that.

v

[WhitPhil]

The multiple passes is done to ensure that none of the data is recoverable. If this were not done, previously written data can be recovered using forensic techniques.

http://en.wikipedia.org/wiki/Gutmann_method

[Jon1001]

Ok, thanks. I think I understand it now.

[JohnWill]

Originally Posted by valis

multiple passes, or 'zero fills', fill every cluster on the hard drive with data, essentially rendering the drive useless.

I'm hoping you don't really mean this, because it just renders the drive "empty", not "useless".

[valis]

Originally Posted by JohnWill

I'm hoping you don't really mean this, because it just renders the drive "empty", not "useless".

I guess a quantifier is necessary. 'Useless' until you put an os on it. Better?

always defer to the sniper cat, and those that have forgot more than I'll learn. But I'm catching ya.....2 more exams, mcse. I swear, I get my hands on the guy who invented binary bits in the subnet, I'll have to borrow the cat.

[JohnWill]

You don't like subnets?

[valis]

seeing as how several hundred dozen of them (and that's just a rough estimate) go along the lines of:

"given the default gateway of 12.68.0.15, provide the subnet and IP address for that segment"

no, I don't really care for them. I created an excel sheet that will convert the ip to binary and back readily, but the problem lies between the ears. Given a sheet of paper, yes, I can figure it out. But during the vendor exam, you are required to figure it out in your head.

To be honest, all it is is a different form of math, and I'm just having problems wrapping my brain around it. It doesn't help when your proctors ALL have different methods for figuring it out. But I'm learning.

Lord knows, there is no way to go but 'up'.