Data Recovery Techniques – SS2 Computer Hardware & GSM Repair Lesson Note (Second Term)

Class: SS2

Subject: Computer Hardware and GSM Repair

Data recovery is the process of finding deleted or lost files and bringing them back. When a file is deleted, the computer only marks its space as empty, so the file stays in place until new data is written over it. Recovery methods depend on where the data is stored.

Behavioural objectives

By the end of the lesson, students should be able to:

• Explain why a deleted file can often be recovered.
• Recover deleted files from a memory card using recovery software.
• Describe why recovery from internal storage is harder than from an SD card.
• Describe the physical recovery methods used on broken or dead phones.
• State the reasons why data recovery sometimes fails.
• Explain why a technician must respect a customer’s privacy.

What happens when a file is deleted?

Have you ever deleted a photo by accident, or formatted a memory card by mistake? When you “delete” a file, it is not gone immediately. The computer hides it and marks the space as “empty” so that something else can be written there later.

As long as no new files are saved over that space, the “ghost” of the old file is still there. Data recovery is the work of finding those files and getting them back.

How do you recover data from a memory card?

Memory cards (SD cards) are the easiest storage to recover data from because they are removable. We can take them out of the phone and plug them directly into a computer.

• The rule of “Stop!”: If you realise you have deleted something from an SD card, take it out of the phone immediately. If you keep taking new photos, the phone will write the new data on top of the old “ghost” files, and they will be destroyed for good.
• The software method: We use special programs such as Recuva, DiskDrill or EaseUS Data Recovery. The steps are:
  1. Plug the card into a PC using a card reader.
  2. Run the software and select the SD card drive.
  3. Click “Deep Scan”.
  4. Preview the found photos and save them to the computer’s desktop. Never save them back onto the same SD card during recovery.

Why is internal storage recovery harder?

Recovering files from the phone’s own internal memory (the built-in 64GB or 128GB) is much harder than recovering from an SD card because of Android’s security.

• The challenge: Modern Android phones use encryption, which means the files are scrambled like a secret code. If the phone is factory reset, the “key” to that code is thrown away, so recovery is almost impossible for a basic technician.
• The “root” method: For many deep recovery tools to work on internal storage, the phone must be rooted. This gives the software “Superuser” permission to look into the hidden parts of the phone.
• Cloud recovery (the smart way): Before you use a computer, always check Google Photos or Google Drive. Many phones automatically back up photos to the internet. If you find the files there, you do not need any complex software.

How is data recovered from a physically damaged phone?

What if the phone is smashed or will not turn on? This is where a GSM technician becomes a surgeon.

• Broken screen: If the phone works but the screen is black, plug in a “test screen” to see the files and move them to a flash drive.
• Dead motherboard: If the board is dead, we use a technique called chip-off recovery. A hot air gun is used to remove the eMMC or UFS chip (the storage chip), which is then placed in a special socket connected to a computer. This is an advanced and expensive skill.

Why does data recovery sometimes fail?

As a student, you must be honest with your customers. You cannot always save everything.

1. Overwriting: If the user kept using the phone for a week after deleting a file, the file is likely overwritten and gone.
2. Factory reset: On new Android versions, a factory reset clears the encryption keys. Even professional tools cannot bring those files back.
3. Physical damage to the chip: If the storage chip itself is cracked or burnt, the data is lost for good.

Which recovery method suits each situation?

Student ethics and privacy guide

Data recovery gives you access to a person’s most private information: their family photos, private messages and bank details. Never look through a customer’s files. Your job is to recover the folder, check that the files open, and then hand it back. Professionalism is about trust.

Evaluation

1. Explain why a deleted file can still be recovered.
2. Why should you take an SD card out of the phone immediately after a file is deleted?
3. List the steps for recovering photos from an SD card using recovery software.
4. Why is recovery from internal storage harder than from an SD card?
5. What is chip-off recovery, and when is it used?

Assignment

1. State the reasons why data recovery sometimes fails.
2. Explain why a technician must never look through a customer’s files during recovery.