Data recovery and destruction are two sides of the same coin. To know when and how you can get your information back, you need to understand how it can be permanently destroyed. And in some situations, it is simply necessary: for example, the destruction of corporate information when disposing of equipment, the destruction of your personal data when transferring a disk for use to friends or selling it, or maybe you want to delete your correspondence history with your mistress once and for all
It is considered that the best specialists in data recovery work in the special services, so we formulated the question in this way: how to delete information from a disk without being recovered by either the K or Q cops in James Bond.
Data destruction by software method
If you still want to use the hard disk after data destruction, and you are not in a hurry, then you should look in the direction of software methods for deleting data.
Complete disk overwrite
There are many algorithms for destroying data by completely overwriting the disk. But they all boil down to N-fold formatting and writing binary ones, zeros, and pseudo-random numbers to it. Since the speed of writing to disk usually does not exceed 70 MB / s, then armed with a calculator, we will calculate how long it will take us?
The formula is quite simple: Disk Size (MB) / Write speed * Number of cycles = Seconds. 500000 / 70 * 7 = 50000 (seconds).
From this, we can conclude that a 500 GB disk will “erase” for about 13 hours. But should we use 7 rewrite cycles? Modern data carriers do not leave any residual magnetization after data rewriting. Therefore, one cycle is enough for us. This means that we will need only 1.5 hours instead of 13 hours.
Operating systems have tools to completely delete files.
Windows:
format c:
Instead of "c:", specify the letter of the logical partition.
Linux:
dd if=/dev/zero of=/dev/sda bs=4k
Instead of "/dev/sda", specify the device address for formatting.
Partial data rewrite
Using a direct connection to the hard disk at the lower level via the disk driver API or your own driver, you can quickly corrupt information by overwriting data gaps with pseudo-random numbers. By directly specifying the memory address to write to, we don't need to completely overwrite the disk. You can also use the disk driver API to get the addresses where information is stored and overwrite only this memory area.
Working with the driver involves 2 stages:
Destroying data along with the disk
Let's complicate the problem: imagine that we don't have time to destroy data safely for the disk. In this case, the only thing that can help you is destroying the disk itself. And to be precise, you only need to destroy the pancakes on which the information is recorded.
Mechanical data destruction
Once and for all, you can destroy the data if you ruin the pancakes of the hard disk. It is difficult and often impossible to recover data from scratched disks, do not forget to keep a screwdriver next to you, because you will have to remove the hard disk cover and it can also scratch the hard disk. Naturally, the data will be erased in the places where the scratch was made and adjacent to it. In other places, the data can be restored in the lab. Do not spare your efforts on scratches, light strips will not destroy data even in places where your screwdriver has been.
But dropping the disk on the floor won't be enough. Yes, it will not be detected by the computer, but the data will be successfully restored in the laboratory. The HDD disk will not survive a fall from the table, and when turned off, the safe fall height is higher than when the disk is running. SSDs were designed for this case, even a fall from a window on the first or second floor will not kill the disk. This is achieved due to the fact that there are no moving elements in the SSD, all actions are performed by the controller.
Modern discs are made of magnetically coated glass. It is enough to remove the disk cover, pull out the magnetic disk and break it. The glass disk breaks easily, but you should take safety measures so as not to cut yourself. If the disk is broken, the entire dusting layer will be destroyed, and it will no longer be possible to restore the data.
Physically
"What doesn't kill us makes us stronger." It is also logical to assume the opposite: what does not make us stronger, kills us. Putting your important data carrier in the freezer doesn't kill it. You have a time bomb in your hands - the disk will work and you can read information from it programmatically. When the disk breaks, all data is easily restored in the “clean room”.
What do disks think about heating up? Among all Yandex. Disk devices, we are only interested in pancakes. The material with which the pancake is covered is able to demagnetize at a temperature of 450 °C. When heated, the magnetic layer should oxidize and turn green. Another negative result for Yandex. Disk, but positive for us, is the temperature of more than 660 °C.
At this temperature, aluminum begins to melt - the basis of a hard disk pancake. A temperature of 750 °C at home can be obtained from a candle flame or a burning match. To reach the maximum temperature, it is necessary to substitute the flame with the very edge to the pancake.
You can also demagnetize the disk using an electromagnet, acting on the pancake with an alternating magnetic field as the distance from the magnet to the disk increases. When they act as pulses on hard disks, they completely demagnetize the disk, which makes it impossible to restore any data on it. These devices destroy everything in 2-3 seconds.
Chemically
As you probably already understood, to destroy data, you need to destroy the magnetic layer of the hard disk pancake. It is enough to pour any liquid that can change the properties of ferromagnets onto the disk. To change the structure of chromium oxide (the ferromagnet that covers hard disk pancakes is the magnetic layer of the disk), you need to pour hydrochloric acid or water on it at a temperature of 100 °C.
What else is important?
It is considered that the best specialists in data recovery work in the special services, so we formulated the question in this way: how to delete information from a disk without being recovered by either the K or Q cops in James Bond.
Data destruction by software method
If you still want to use the hard disk after data destruction, and you are not in a hurry, then you should look in the direction of software methods for deleting data.
Complete disk overwrite
There are many algorithms for destroying data by completely overwriting the disk. But they all boil down to N-fold formatting and writing binary ones, zeros, and pseudo-random numbers to it. Since the speed of writing to disk usually does not exceed 70 MB / s, then armed with a calculator, we will calculate how long it will take us?
The formula is quite simple: Disk Size (MB) / Write speed * Number of cycles = Seconds. 500000 / 70 * 7 = 50000 (seconds).
From this, we can conclude that a 500 GB disk will “erase” for about 13 hours. But should we use 7 rewrite cycles? Modern data carriers do not leave any residual magnetization after data rewriting. Therefore, one cycle is enough for us. This means that we will need only 1.5 hours instead of 13 hours.
Operating systems have tools to completely delete files.
Windows:
format c:
Instead of "c:", specify the letter of the logical partition.
Linux:
dd if=/dev/zero of=/dev/sda bs=4k
Instead of "/dev/sda", specify the device address for formatting.
Partial data rewrite
Using a direct connection to the hard disk at the lower level via the disk driver API or your own driver, you can quickly corrupt information by overwriting data gaps with pseudo-random numbers. By directly specifying the memory address to write to, we don't need to completely overwrite the disk. You can also use the disk driver API to get the addresses where information is stored and overwrite only this memory area.
Working with the driver involves 2 stages:
- The first is to get the address and length of data. Usually one file is written in different places on disk, so we will get an array of addresses and an array of lengths.
- The second step is to write pseudorandom numbers to these memory areas. You must also write them through the driver, so that the operating system does not block or redirect data writing to another area of the disk.
Destroying data along with the disk
Let's complicate the problem: imagine that we don't have time to destroy data safely for the disk. In this case, the only thing that can help you is destroying the disk itself. And to be precise, you only need to destroy the pancakes on which the information is recorded.
Mechanical data destruction
Once and for all, you can destroy the data if you ruin the pancakes of the hard disk. It is difficult and often impossible to recover data from scratched disks, do not forget to keep a screwdriver next to you, because you will have to remove the hard disk cover and it can also scratch the hard disk. Naturally, the data will be erased in the places where the scratch was made and adjacent to it. In other places, the data can be restored in the lab. Do not spare your efforts on scratches, light strips will not destroy data even in places where your screwdriver has been.
But dropping the disk on the floor won't be enough. Yes, it will not be detected by the computer, but the data will be successfully restored in the laboratory. The HDD disk will not survive a fall from the table, and when turned off, the safe fall height is higher than when the disk is running. SSDs were designed for this case, even a fall from a window on the first or second floor will not kill the disk. This is achieved due to the fact that there are no moving elements in the SSD, all actions are performed by the controller.
Modern discs are made of magnetically coated glass. It is enough to remove the disk cover, pull out the magnetic disk and break it. The glass disk breaks easily, but you should take safety measures so as not to cut yourself. If the disk is broken, the entire dusting layer will be destroyed, and it will no longer be possible to restore the data.
Physically
"What doesn't kill us makes us stronger." It is also logical to assume the opposite: what does not make us stronger, kills us. Putting your important data carrier in the freezer doesn't kill it. You have a time bomb in your hands - the disk will work and you can read information from it programmatically. When the disk breaks, all data is easily restored in the “clean room”.
What do disks think about heating up? Among all Yandex. Disk devices, we are only interested in pancakes. The material with which the pancake is covered is able to demagnetize at a temperature of 450 °C. When heated, the magnetic layer should oxidize and turn green. Another negative result for Yandex. Disk, but positive for us, is the temperature of more than 660 °C.
At this temperature, aluminum begins to melt - the basis of a hard disk pancake. A temperature of 750 °C at home can be obtained from a candle flame or a burning match. To reach the maximum temperature, it is necessary to substitute the flame with the very edge to the pancake.
You can also demagnetize the disk using an electromagnet, acting on the pancake with an alternating magnetic field as the distance from the magnet to the disk increases. When they act as pulses on hard disks, they completely demagnetize the disk, which makes it impossible to restore any data on it. These devices destroy everything in 2-3 seconds.
Chemically
As you probably already understood, to destroy data, you need to destroy the magnetic layer of the hard disk pancake. It is enough to pour any liquid that can change the properties of ferromagnets onto the disk. To change the structure of chromium oxide (the ferromagnet that covers hard disk pancakes is the magnetic layer of the disk), you need to pour hydrochloric acid or water on it at a temperature of 100 °C.
What else is important?
- If you don't need long - term storage of confidential data-write them to volatile (random access) memory, then you don't have to worry about destruction.
- Make sure that you can't restore your data from any other media that has ever been copied to.
- Be careful when transmitting data over the network. Use cryptographic protection devices. If your information remains on the server, then destroying it from your media will not protect it in any way. In this case, it makes sense to encrypt the information stored in the cloud with special software.
