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How secure is file wiping? An analysis of file recovery chances based on wiping methods and the number of overwrites

How secure is file wiping? An analysis of file recovery chances based on wiping methods and the number of overwrites
March 07, 2023

File wiping is the process of securely deleting data from a storage device, such as a hard disk or solid-state drive (SSD), to ensure that unauthorized users cannot recover it. However, the effectiveness of file wiping can vary depending on the wiping method used and the number of times the data has been overwritten.

Wiping Methods:
There are several methods of file wiping, including simple deletion, single overwriting, multiple overwriting, and physical destruction. Simple deletion involves deleting a file using the operating system's delete function, which marks the file as deleted and does not remove the data from the storage device. This method is insecure and can be easily reversed using file recovery software.

Single overwriting involves overwriting the file once with a specific pattern, such as zeros or ones. This method is more secure than simple deletion, but there is still a chance that some of the original data can be recovered using specialized software.

Multiple overwriting involves overwriting the file multiple times with different patterns, making it more difficult to recover the original data. The number of overwrites required to make the data irrecoverable depends on the sensitivity of the data and the necessary level of security.

Physical destruction involves physically destroying the storage device, such as shredding, burning, or melting it. This method is the most secure but is also the most extreme and is generally only used for highly sensitive data.
 

Chances of File Recovery:
The chances of recovering a file that has been securely wiped depend on several factors, including the wiping method used, the number of overwrites, and the type of storage device used. Simple deletion offers no protection against file recovery, as the data is still present on the storage device and can be easily recovered using file recovery software.

Single overwriting offers some protection against file recovery, but there is still a chance that some of the original data can be recovered using specialized software. However, the likelihood of recovery decreases with each additional overwrite.

Multiple overwriting is generally considered to be a more secure method of file wiping, as it makes it more difficult to recover the original data. The likelihood of recovery decreases with each additional overwrite, and after a certain number of overwrites, the chances of recovery become vanishingly small.


If a file has been securely wiped using a method such as the 0xff method and the hard disk is not too old, the chances of recovering the wiped file are generally very low, even if the file has only been overwritten once. Furthermore, the likelihood of recovering the file decreases further with each additional overwrite.

Here are some rough estimates of the chances of recovering a wiped file from a hard disk that has not been physically destroyed based on the number of times the file has been overwritten:

  • 1 overwrite: Chances of recovery are less than 1%
  • 3 overwrites: Chances of recovery are less than 0.1%
  • 4 overwrites: Chances of recovery are less than 0.01%
  • 5 overwrites: Chances of recovery are less than 0.0001%
  • 8 overwrites: Chances of recovery are less than 0.00000001%

It is worth noting that these estimates are based on various assumptions and are not exact. The chances of recovering a wiped file depend on many factors, and it is impossible to predict the chances with 100% accuracy.
 

Erasure Algorithms:
There are several erasure algorithms commonly used for securely wiping data. Some of the most common erasure algorithms include:

  • Gutmann method: This method was developed by Peter Gutmann in 1996 and involves overwriting data 35 times with different patterns. While it is considered to be a very secure wiping method, it is also considered to be overkill for most scenarios.
  • DoD 5220.22-M: This method was developed by the U.S. Department of Defense and involves overwriting data three times with different patterns. It is commonly used by government agencies and is considered to be a very secure wiping method.
  • Random Data method: This method involves overwriting data multiple times with random data. The number of overwrites required on the sensitivity of the data and the level of security needed.
  • Write Zeroes method: This method involves overwriting data with zeroes one or more times. While it is a simple and effective wiping method, it is not considered as secure as other wiping methods that use multiple overwrites and different patterns.
     

Several international standards define erasure methods and requirements for securely wiping data. Some of the most widely recognized standards include:

  • NIST SP 800-88: This standard was developed by the National Institute of Standards and Technology (NIST) in the U.S. and provides guidelines for media sanitization, including the selection and application of media sanitization techniques.
  • ISO/IEC 27040: This standard was developed by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) that provides guidelines for the storage of digital information, including requirements for the secure erasure of data. The standard is intended to help organizations manage the confidentiality, integrity, and availability of their information assets.
  • HMG Infosec Standard 5: This standard was developed by the U.K. government and provides guidance on the secure destruction of digital media.

 

By following these standards, organizations can ensure that they are using industry-approved methods for securely wiping data and protecting sensitive information.

An erasure algorithm that encrypts and wipes data can provide an extra layer of security, as it makes it more difficult for anyone to recover the original data, even if they manage to recover the overwritten data. However, it is important to choose an encryption algorithm that is strong enough to provide adequate protection and to use a secure wiping method in addition to encryption.

There is no hard and fast rule regarding the number of overwrites required to erase data securely. However, in general, the more times data is overwritten with different patterns, the lower the chances of recovering the original data.

If you use a wiping method that overwrites data 9-50 times, the chances of recovering the original data would be lower than for methods that overwrite data fewer times. However, if the data is overwritten enough times with different patterns, the chances of recovering the original data become vanishingly small, even for the most advanced recovery techniques.

However, the exact number of overwrites required to erase data securely depends on various factors, including the type and age of the storage media and the expertise of the forensic expert attempting to recover the data. Therefore, if you need to ensure that your data is completely irrecoverable, it is recommended to use multiple wiping methods and/or physically destroy the storage media to ensure that the data is completely destroyed.

In summary, file wiping is a crucial process to delete data securely, but its effectiveness depends on several factors. Using multiple wiping methods, modern erasure algorithms, and physically destroying the storage media can ensure the data is completely irrecoverable. For more information, visit the iShredder website for advanced secure deletion algorithms and securely erasing data.

 

Learn more
Securely erase data with iShredder: https://www.protectstar.com/en/products/ishredder
Advanced Secure Deletion Algorithm: https://www.protectstar.com/en/secure-erase
 

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