Ever wondered why it takes time to copy a large file from one disk to another disk, but deleting the file takes a fraction of a second? That's because the file isn't really getting deleted. Only it's address is being erased. The actual file is still there on the disk, and there are software which can recover the file by identifying the sectors on the disk that the data is stored in, even if the data is not contiguous (stored in sectors that are one after another). This is why, even when a disk has no partitions and you think there is no data on it, the files that are there on the disk can still be recovered. The storage of data on SSD's or pen drives or your phone's storage works a bit differently from how data is stored on magnetic disks like the HDD. To know more about how long data can be retained on each type of disk and how data gets corrupted and how it can be recovered, read on...
1. Magnetic Hard Disk Drives (HDDs)
Technology and Material:
HDDs use magnetic storage to record data. A spinning disk coated with a magnetic material (typically iron oxide or cobalt alloys) is used to store data in binary format. Read/write heads move over the disk to magnetize tiny areas, corresponding to data.
Data Persistence:
Data on HDDs can last anywhere from 3 to 10 years depending on the quality of the drive and storage conditions. Environmental factors such as heat and humidity can reduce the lifespan of the drive. So if sectors on the disk lose their magnetism, data can get corrupted. It helps to copy fresh data onto the disk or overwrite the disk with random numbers and then freshly re-copy your data onto the disk every 3 to 5 years.
Factors That Can Corrupt Data:
- Physical shock or damage
- Power surges
- Magnetic fields
- Mechanical wear (moving parts failure)
Data Recovery Tools:
- Windows:
- CHKDSK (Command Line):
chkdsk X: /f - Recuva (GUI Tool for recovery)
- CHKDSK (Command Line):
- Linux:
- TestDisk and PhotoRec (Command Line):
sudo testdisk - PhotoRec (Command Line for recovery of lost files)
- TestDisk and PhotoRec (Command Line):
- Mac:
- Disk Utility (GUI)
- PhotoRec (Command Line)
Secure Deletion Tools:
- Windows:
- SDelete (Command Line):
sdelete -p 3 X:
- SDelete (Command Line):
- Linux:
- Shred (Command Line):
shred -u X
- Shred (Command Line):
- Mac:
- srm (Command Line):
srm -v X
- srm (Command Line):
Common Assumptions About Deletion:
Many people assume that simply deleting files from an HDD removes them permanently. In reality, deleted files are often recoverable until they are overwritten by new data.
2. Solid State Drives (SSDs)
Technology and Material:
SSDs use NAND flash memory, a non-volatile memory type that stores data in floating-gate transistors. Data is stored in blocks, which are electrically erased and rewritten.
Data Persistence:
The data on SSDs can last 5 to 10 years, but it depends on the number of write/erase cycles the cells go through. SSDs can wear out over time due to this limitation, often referred to as write endurance.
Factors That Can Corrupt Data:
- Excessive write/erase cycles
- Power failures during write operations
- Physical damage (e.g., exposure to heat or static electricity)
Data Recovery Tools:
- Windows:
- Recuva (GUI tool)
- Linux:
- ddrescue (Command Line):
sudo ddrescue /dev/sdX /path/to/backup.img - TestDisk and PhotoRec
- ddrescue (Command Line):
- Mac:
- Disk Drill (GUI)
- PhotoRec (Command Line)
Secure Deletion Tools:
- Windows:
- SDelete (Command Line)
- Linux:
- blkdiscard (Command Line):
sudo blkdiscard /dev/sdX
- blkdiscard (Command Line):
- Mac:
- diskutil secureErase (Command Line):
diskutil secureErase freespace 0 /Volumes/DriveName
- diskutil secureErase (Command Line):
Common Assumptions About Deletion:
SSD users often believe that wiping the data using conventional methods like formatting or deleting files ensures security. However, because of the wear leveling algorithm, deleted data can still be accessible, requiring specialized tools like blkdiscard for secure erasure. Even overwriting a file with the same filename, won't overwrite data on the same location. Remember that.
3. USB Flash Drives / Pen Drives
Technology and Material:
Pen drives use NAND flash memory (similar to SSDs). Data is stored in arrays of transistors, and the device is accessed via a USB interface.
Data Persistence:
Data on flash drives can last from 5 to 10 years, depending on usage. Like SSDs, repeated write/erase cycles can degrade their lifespan.
Factors That Can Corrupt Data:
- Physical damage
- Power surges or interruptions during writing
- Data corruption due to improper ejection
Data Recovery Tools:
- Windows:
- Recuva (GUI)
- DiskPart (Command Line for disk partition issues)
- Linux:
- TestDisk (Command Line)
- PhotoRec (Command Line)
- Mac:
- Disk Utility (GUI)
- Disk Drill (GUI)
Secure Deletion Tools:
- Windows:
- SDelete (Command Line)
- Linux:
- shred (Command Line)
- wipe (Command Line):
wipe /dev/sdX
- Mac:
- diskutil (Command Line):
diskutil secureErase 0 /dev/diskX
- diskutil (Command Line):
Common Assumptions About Deletion:
Many assume that formatting a USB drive removes all data securely. However, like SSDs, some data might still be recoverable unless specifically erased using secure deletion tools.
4. SD Cards (Secure Digital Cards)
Technology and Material:
SD cards, commonly used in cameras and smartphones, also use NAND flash memory. They provide fast read/write speeds and are more durable than hard drives due to the absence of moving parts.
Data Persistence:
Data can last 5 to 10 years, with performance degradation over time, especially after many read/write cycles.
Factors That Can Corrupt Data:
- Physical damage (e.g., water exposure)
- Power loss during data transfer
- Incorrect ejection or unsafe removal
Data Recovery Tools:
- Windows:
- Recuva (GUI)
- Linux:
- TestDisk (Command Line)
- PhotoRec (Command Line)
- Mac:
- Disk Utility (GUI)
- Disk Drill (GUI)
Secure Deletion Tools:
- Windows:
- SDelete (Command Line)
- Linux:
- shred (Command Line)
- wipe (Command Line)
- Mac:
- diskutil secureErase (Command Line)
Common Assumptions About Deletion:
Formatting or deleting files from an SD card does not securely erase the data. If you intend to sell or dispose of an SD card, be sure to use tools designed to overwrite and securely delete the data.
5. Blu-ray Discs, DVDs, and CDs
Technology and Material:
Optical media such as Blu-ray discs, DVDs, and CDs use laser beams to read and write data onto a reflective surface. Blu-rays have higher storage capacity (25GB or more), while CDs and DVDs have lower capacities (700MB for CDs, 4.7GB for DVDs).
Data Persistence:
Optical media can store data for up to 10 to 50 years, but this varies depending on the quality of the disc and the environmental conditions in which it's stored (heat, humidity, and exposure to light).
Factors That Can Corrupt Data:
- Scratches or physical damage to the disc
- Exposure to sunlight, heat, or humidity
- Laser errors during reading or writing
Data Recovery Tools:
- Windows:
- IsoBuster (GUI)
- Linux:
- ddrescue (Command Line)
- Mac:
- Disk Utility (GUI)
Secure Deletion Tools:
- Windows:
- No standard tools for physical media erasure; consider overwriting via file system tools
- Linux:
- Shred (Command Line) for files on the disc, but no tool for erasing the disc itself.
- Mac:
- diskutil eraseDisk (Command Line) to erase the entire disk.
Common Assumptions About Deletion:
People often assume that wiping files off a disc is enough to remove them permanently. However, optical media is physically written, so the data can still be retrieved through specialized tools even after deletion, unless physically destroyed.
Remember: deletion is not the end of the story. Use secure erasure tools to ensure your data stays gone—permanently! There are more tools that I have not mentioned here. Searching the internet will show you more. Most of this blog post was written by AI.
