Добавил:
Upload Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз: Предмет: Файл:
2010 пособие для ФИТТ1.doc
Скачиваний:
305
Добавлен:
10.06.2015
Размер:
2.81 Mб
Скачать

Shadow data (part 1) [1]

Task 1. Read and translate the text:

Задание 1. Прочитайте и переведите текст:

Have you ever thought about why some government agencies require computer data to be erased by overwriting it at least seven times or even more? Have you ever thought why classified (or secret) government agencies prefer to destroy computer hard disk drives rather than surplus them? The reasons for these levels of paranoia are valid and they are connected with the potentials of security breaches tied to shadow data.

When computer data is written to a floppy disk, zip disk, hard disk or tape, a mechanical device called a head is used to write the data. The information is stored electronically in magnetic patterns of binary ones and zeros. The patterns are in the form of sectors which are written consistently in concentric rings called tracks. The process is fast and efficient. However, it also involves the use of a mechanical device which operates with less than exact tolerance levels. Horizontal head straightening and vertical head placement is just a bit different every time the information is written and rewritten to the same track. This situation limits the effectiveness of software data scrubbers and it creates the potential for government security breaches on well used storage devices. Thus, government agencies require multiple writes when data is destroyed with data scrubbers. However, even multiple writes can not guarantee complete removal of legacy data. The last data that remains on the track is called shadow data. However, NTI’s M-Sweep Pro Software removes almost all potentials for the forensic recovery of shadow data.

Shadow data contains the leftovers of computer data that was written previously to a track and it is located slightly outside the track's last recording path. It gets a bit more complicated though. There are actually two reasons which cause shadow data to come about: mechanical issues and magnetic issues. To illustrate the mechanical issues, imagine a long, straight road of a consistent width. A car traveling along that road has a paint sprayer attached to its bumper, and paints a line as it goes. Mechanical shadow data manifests itself due to imperfections in the drive's servomechanism which causes the write arm, which holds the write head over the drive's surface, to shake horizontally to the left and right to a certain extent. This would be analogous to our vehicle weaving back and front on the road as the paint sprayer continues doing its job. The resulting painted line would not be in a straight line, but something like elongated "s" pattern. Each pass of the write head varies slightly creating new elongated "s" patterns within the bounds of the storage space assigned to the track.

The source of magnetic shadow data is analogous to the paint sprayer's nozzle being moved up and down vertically as the line is painted. If it is high, the paint spray pattern will be wide. If it is low, the paint pattern will be narrow and the painted line will be thin. With this analogy the paint over spray would be shadow data which would not be completely covered if a new line were to be painted on the road. This splatter effect is actually caused by variances in signal strength as the head moves up and down vertically as the data is written to the track.

Task 2. Answer the following questions:

Задание 2. Ответьте на следующие вопросы:

  1. Why do secret agencies need to erase by overwriting data many times?

  2. What device is used to write data on floppy, zip or hard disks?

  3. How hard disk is arranged?

  4. What is the shadow data?

  5. What are the phenomena of shadow data to come about?

  6. How you can illustrate the mechanical issues of shadow data?

  7. What is the source of magnetic shadow data?

Task 3. Find the English equivalents of the words given below in the text and make sentences with them:

Задание 2. Напишите определения следующих терминов и составьте с ними предложения:

hard disk drive, floppy diskette, zip disk, hard disk, software data, storage space.

Task 4. Match the words:

Задание 4. Соедините слова из левой и правой колонок таким образом, чтобы получить терминологические сочетания:

data

device

alignment

head

placement

horizontal

storage

electronic

Task 5. Say whether the statements given below are true or false:

Задание 5. Определите истинность или ложность следующих предложений:

1. When computer data is written to a floppy disk, zip disk, hard disk or tape, a mechanical device called a head is used to write the data.

2. The information is stored electronically in magnetic patterns of binary ones and zeros.

3. Horizontal head straightening and vertical head placement is just the same every time the information is written.

4. Multiple writes can guarantee complete removal of legacy data.

5. There is only one reason which causes shadow data to come about.

Task 6. Complete the sentences according to the text:

Задание 6. Закончите предложения:

1. The reasons for these levels of paranoia are ... .

2. The information is stored electronically in ... .

3. However, it also involves the use of a mechanical device

which ... .

4. Thus, government agencies require ... .

5. The last data that remains on the track is ... .

6 .... can not guarantee complete removal of legacy data.

7. ... removes almost all potentials for the forensic recovery of shadow data.

8. ..... that was written previously to a track and it is located slightly outside the track's last recording path.

Task 7. Translate the sentences from Russian into English:

Задание 7. Переведите с русского языка на английский:

1. В результате, линия будет не прямой, а похожей на удлиненную букву «s».

2. Каждое движение пишущей головки немного разнится, создавая новый образец этой удлиненной «s» в границах памяти, выделенной на дорожку.

LESSON 24

Соседние файлы в предмете [НЕСОРТИРОВАННОЕ]