1. ▹ Antivirus
  2. ▹ Assets
  3. ▹ Authentication
  4. ▹ Availability
  5. ▹ Basic criteria for risk analysis
  6. ▹ Computer Hacks
  7. ▹ Confidentiality
  8. ▹ Control
  9. ▹ Cryptography
  10. ▹ Cybercrime
  11. ▹ Cybercriminals
  12. ▹ DRP – Disaster Recovery Plan
  13. ▹ Data backups
  14. ▹ Data loss
  15. ▹ Defacement
  16. ▹ Disinfect machine with a live CD
  17. ▹ Disposal
  18. ▹ Email
  19. ▹ Firewall
  20. ▹ Human error
  21. ▹ IDS/IPS
  22. ▹ Image rights
  23. ▹ Impact
  24. ▹ Integrity
  25. ▹ Internet and copyright
  26. ▹ Legal Aspects
  27. ▹ LuxTrust
  28. ▹ Malicious Codes
  29. ▹ Malicious websites
  30. ▹ Network segmentation
  31. ▹ Password
  32. ▹ Patches
  33. ▹ Phishing
  34. ▹ Physical faults
  35. ▹ Securing a fixed workstation
  36. ▹ Physical theft
  37. ▹ Recommendations for securing a file server
  38. ▹ Recommendations to secure a server connected to Internet
  39. ▹ Recommendations to secure a Web server
  40. ▹ Removable devices
  41. ▹ Risk processing
  42. ▹ Spam – unwanted emails
  43. ▹ SSL/TLS – encryption technologies on the web
  44. ▹ Update softwares with Secunia PSI
  45. ▹ Security Charter
  46. ▹ Social engineering
  47. ▹ Threat
  48. ▹ Virtual Private Networks (VPNs)
  49. ▹ Vulnerabilities
  50. ▹ Web of Trust - WOT
  51. ▹ Web filter – Proxy
  52. ▹ Why is it important to protect your computer?


In brief

Data that belongs to you or which you process using your computer has different levels of confidentiality. You probably don’t treat data you post on social networks and that which you keep solely on your hard drive in the same way. Customer information, your company’s strategic data, texts, letters or emails constitute only the visible part of your behaviour on the computer. In addition to that, a certain amount of data is generated as a secondary product during such use: temporary files, browser history, user profiles and saved passwords are just a few examples. You therefore need to bear in mind that when you use a computer, you leave behind a trace, like a snail, of everything you have done.

If you would like to scrap your computer or pass it on to someone else, it is important to get rid of these traces entirely. Simply deleting the files or reformatting the hard drive is not enough. The section below will tell you what you need to know in advance.

For classified data, such as confidential data, we recommend total physical destruction by a crusher or a demagnetiser. Passing on this equipment to someone else is out of the question.

Total destruction of your data


You want to resell or scrap your PC. The hard drives containing your data are going to fall into unknown hands. You need to delete everything.

Procedure to follow

To effectively delete all the aforementioned data, it is important to use a different system to the one you want to get rid of. You could, for example, remove the drives and connect them to another computer. The easiest way to do this, however, consists of using a “live” system that can restart your computer without using its internal hard drives.

The “Darik’s Boot and Nuke” live system is available free of charge from the following website:

Please download the file with the “iso” extension. This file resembles a compact disc that is ready to be burned. To use it, you simply need to use burning software. Take care not to burn your CD as a conventional data disk with the image file as the contents, but search for the “burn image” option.

Once the CD has been burned, you’ll need to restart your computer with the CD in the CD ROM drive. On most computers, the disk will be launched at start-up instead of the operating system. If your usual operating system loads instead of “Darik’s Boot and Nuke”, you’ll have to put the CD ROM drive first in the boot order in your BIOS settings. We recommend you use an Internet search to help you set up this configuration.

Data destruction

Once this live CD has started up, type autonuke[enter] to delete all your computers’ hard drives. Please note that this will also destroy the memories of any mass storage devices connected to the computer by USB (such as cameras or external hard drives). You will then be able to return to your usual activities. As this process can take a while, make sure you leave your computer on continuously for at least one day.

Generally speaking, for magnetic media (conventional hard drives) the “Quick Erase” method should be sufficient. It also has the advantage of being the fastest process.

It is important to note that the only method you should use for flash memory (and therefore SSD drives) is the “Quick Erase” method. Other methods could damage this type of drive and wouldn’t be effective as they are best suited to magnetic media.

After destruction

Depending on what you plan to do with your computer, you can now reinstall your favourite operating system or get rid of your computer without any concerns.


Effective process which requires little interaction.


Lengthy process. For a company looking to destroy a lot of hard drives, physical destruction will be the fastest (and possibly cheapest) route.

Targeted destruction of data


You want to give your PC to someone you trust, perhaps one of your children. The method described above is particularly applicable if you have lost your PC’s re-installation disk and you would like to give them an operational computer. The aim is to delete confidential data while leaving the operating system intact.

Nevertheless, the targeted destruction of existing data has some major drawbacks, because not only will traces of your data remain forever, but this method also won’t destroy any malicious software that may have made its way onto your computer and you risk passing on an infected computer to one of your family or friends.

Procedure to follow

In addition to the tools you already have on your computer, we’re going to use the following software: ccleaner – downloadable from

Data destruction

All Windows systems come with an Administrator account by default. Close your current session Start -> Log off. The Windows Logon screen will appear. Unfortunately, the Administrator user account is hidden. You’ll need to press CTRL + ALT + DELETE to make the classic logon screen appear.

This special user is called Administrator in the English (and German) version of Windows (or Administrateur in French). If you cannot remember the Administrator password, we recommend you create a new user with administrator privileges and use this one. The main thing is that you’re not logged on with your usual account.

Right click on My Computer, then select Manage:

Now select your usual accounts and delete them by pressing the DELETE key:

Then delete the personal directory for the deleted accounts which is located at C:\Documents and Settings\ or C:\Users\ for more recent versions of Windows:

Next, it is important to uninstall software that you don’t want to pass on, due to user licences for example. It is possible to use Windows’ integrated uninstall features, but ccleaner is noticeably faster. So, launch ccleaner:

Remember to delete any WiFi passwords by going to Control Panel and looking for Network Connections. Right click on your network connection:

Go to Properties, then the Wireless Network tab

In Windows 7 and Vista, look for the wireless network manager in Control Panel, where you can select the networks and delete them.

Now remember to delete your restore points. Right click on My Computer, then select System Properties:

Then choose the System Protection tab and System Restore to deactivate this feature. Once you’ve clicked OK, your restore points will be deleted.

If you want to go even further, clear the virtual memory pagefile, which may contain snippets of compromising memory by going to the Advanced tab, click on the Settings button in Performance, Advanced tab, virtual memory. This last stage isn’t very important and you can ignore it if you wish.

If you still have data stored in other locations, it is important to delete it now. Select the folders or files to be deleted and hold down the [shift]+[delete] keys to delete them without sending them to the recycle bin. If you have deleted the files the conventional way, just remember to empty the recycle bin.

Then delete all hidden data using ccleaner:

The default settings should be sufficient given that you’ve deleted the main user profile.

All deleted data can in theory be recovered from the free space on the hard drive. Use ccleaner to clear the free space:

After destruction

You can now create an account for the new user.


Process doesn’t require a system re-installation.


Process doesn’t guarantee the total destruction of data. Additionally, if the computer has previously been infected by malware, this won’t have been removed from the system.


We have given you two ways of removing data from a PC. We strongly recommend you use the first method, which guarantees:

  1. the total removal of data;
  2. a malware-free system after re-installation.

Removal is easier, but takes longer than the second method. On the other hand, of you want to pass on an operational computer, you will need to reinstall the operating system.

A third very effective way is obviously to crush or demagnetise at least your hard drive, if not your computer. This is a very safe solution which is perfect for large volumes and, therefore, for companies. Some companies specialise in the destruction of data, and it is better to pay for them to be destroyed than have them stolen.

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