問72
頻出度★★★
PC やハードディスクを譲渡したり返却したりする前に実施しておくこととして, ハードディスクからの情報漏えいを防ぐ最も確実な方法はどれか。
平成22年度 春期 ITパスポート試験 問72
This question's explanation and your answers so far.
解説
問 72
- ア
正解 The correct answer is ア. To truly prevent information leakage from a hard disk, the area where the data itself is recorded must be filled over with different values so that the original data can no longer be read out physically. If the entire disk is overwritten several times with hexadecimal 00 or FF, or with random numbers, the magnetic patterns recorded before are completely replaced by different ones, so the original data cannot be retrieved even with file recovery software. This processing is called data erasure (data wiping), and it is normally carried out with dedicated erasing software. It is repeated several times in order to rule out the possibility that the original data could be inferred from residual magnetism after only one overwrite, and it can be called the most reliable method required when a disk passes into someone else’s hands, as in a transfer or a return.
Incorrectイ
A logical format only initializes the areas that manage where files are located (directory information and management tables), making the disk look empty. The areas where the data itself was recorded are not overwritten and remain as they were, so the original files can be retrieved with recovery software. Even though it looks empty, the risk of information leakage remains.
Incorrectウ
Emptying the recycle bin only makes the OS delete the management information of those files and mark the areas as reusable; the data itself keeps sitting on the disk until it is overwritten. It can easily be read out with recovery software, so it is entirely insufficient as a measure before a transfer.
Incorrectエ
A password lock is a mechanism that restricts access to the disk, while the data itself remains exactly as it was. If the password is broken or released, the contents can be read out; moreover, a disk that has been transferred or returned is meaningless if the other party cannot use it. Since the data has not been erased, this cannot be called the most reliable method.
ここがポイント
- Deleting files, emptying the recycle bin, and performing a logical format all merely erase the management information of files, while the data itself stays on the disk. Since it can be read out with recovery software, none of them works as a measure against information leakage.
- Reliable data erasure is done by overwriting the entire disk several times with 00, FF, random numbers, and the like so that the data itself is destroyed (using dedicated data-erasing software). When a disk is to be disposed of, it is also worth remembering the method of physically destroying it.