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How to Securely delete data
Published  06/13/2011 | Security | Rating:
How to Securely delete data

The reasons for deleting files are many: Freeing disk space, removing unnecessary or unneeded data, even making sensitive data unavailable to others. However, securely deleting data involves more than simply emptying the Recycle Bin. Basic file deletion methods only remove he direct pointers to data disk centres. A residual form of the data, called data remanence, still persists. Thus, any one with data recovery tools can still unearth the data once more. Physical destruction may seem like the only way but thankfully, there exist many data erasure methods that remove information permanently while still keeping the disk operable.

Software-based overwriting is one such method. It writes patterns of meaningless data onto each of a hard drive’s sectors. It differs from pure data erasure in that some data will still be intact and at risk of data breach or information theft. Nonetheless, data erasure employs multiple overwrites according to different overwriting standards. There are usually three types of data erasure that differ depending on the number of overwrites:
1. Fast erasure – Consists of one round of data deletion and the filling of space with random data.
2. Forced erasure – A US Department of Defense standard of file erasure. Unlike quick erase, data is overwritten with useless info 3 to 7 rounds in a row. Also referred to as the DoD 5220.22M Standard.
3. Ultimate erasure – The erased file goes through 35 rounds of overwriting, first with a lead-in four random write patterns, 5-31 patterns executed in random order and a lead-out of four more random patterns. This method is also referred to Gutmann Algorithm.

The data overwriting the existing data consists of little more than random numbers or a series of zeroes and ones bit patterns. Freeraser: Free Shredder is a Windows file shredding utility that wipes files in all three of the above methods and is good for basic use. It even places a fancy recycle bin icon that prompts a warning message any time you drag any data to it. Eraser Secure Data Removal Tool goes even further by can also erase space allocated to the file by the OS (called file slack space), Windows virtual memory swap files, unused space on a hard disk or an entire hard disk and also erasing filenames from the directories. It can wipe any amount of data specified and even supports the
three above erasure methods. It’s also open source and works
perfectly with Windows.

Let’s say you want to completely wipe your hard disk, when giving away your computer to someone for example. No other software is best suited for bulk emergency destruction than Darik’s Boot and Nuke, referred to as DBAN for short. It comes in the form of bootable CDROM image and once loaded proceeds to completely destroy data in every partition and hard disk.

A PC can have more than one user. For more than one user, especially with children, it’s always good to keep more than one user profile. However, it’s important to specify which files a user can be allowed to access and manipulate. Windows usually keeps most important system files hidden but they can still be modified. Hence, controlling accessibility becomes a major part of computer security especially when your computer is cracked. To modulate accessibility, first go to the Control Panel >User Accounts and make sure more than one account is active (preferably one with administrator access and one “guest” account). Then right-click on the My Computer icon, select Properties and go to the Advanced tab. Options for Performance, User Profiles and Start-up & Recovery will be available. Select User Profiles and depending on your accounts set, you can specify which drives different users will access. You can also set up groups to decide who can access which drives and documents.

Creating a Limited access account, with no access to the important system files has its advantage on open networks and wi-fi connections. Sharing networks over a wi-fi easily allows another user to access one’s files and hard drives for malicious purposes. Viruses and spyware present on the main server system will also infect other computers in the network. You should have an anti-virus, anti-spyware and firewall installed on the system. But locking out access to the vital system files will eliminate the extra 1% of intrusions that make it through.

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