How to Export File Hashes to CSV in Windows using PowerShell

Learn how to export SHA-256 and MD5 hashes of files in a directory to a CSV file using PowerShell scripts. Protect your data integrity by keeping track of file changes.
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Ensuring File Integrity with PowerShell: Exporting File Hashes to CSV

When dealing with files received from clients, it's critical to maintain the integrity of those files. A common concern is the possibility of tampering after processing, especially if the original content needs to be altered. In this guide, we'll explore how to generate a report of the hashes (SHA-256 and MD5) of files in a directory and export that information to a CSV file using PowerShell. This will help you verify file integrity while keeping a backup of their original state.

Why Hashing?

Hashing is a method used to create a unique identifier for a file. Simple changes to a file will produce entirely different hash values, making it an effective way to verify that a file has not been tampered with. The two popular hashing algorithms we will focus on are:

SHA-256: A widely used hashing algorithm known for its security.

MD5: An older, faster hash algorithm, but less secure than SHA-256.

By exporting these hashes to a CSV file, you’ll have a reliable reference for each file's integrity over time.

Getting Started: Exporting Hashes from a Single Directory

To begin, we will export the SHA-256 hashes of all files in a specific directory. Open PowerShell and use the following command:

[[See Video to Reveal this Text or Code Snippet]]

Breakdown of the Command:

Get-ChildItem: Lists all files in the current directory.

Get-FileHash: Computes the hash value for each file listed.

Export-CSV: Exports the results to a CSV file at the designated path.

Example Output

After executing the command, you can view the contents of your CSV file using:

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The output will be similar to:

[[See Video to Reveal this Text or Code Snippet]]

Exporting Both SHA-256 and MD5 Hashes

If you need to collect both SHA-256 and MD5 hashes for a comprehensive report, you can use the following script:

[[See Video to Reveal this Text or Code Snippet]]

Understanding the Script:

Storing SHA-256 hashes: First, we retrieve the SHA-256 hashes and store them in the variable $h.

Calculating MD5 hashes: Using the same list of files, we compute their MD5 hashes and store them in $h2.

Creating a Custom Object: For each file, we create a custom object that holds the file path, SHA-256, and MD5 hashes.

Example Output for Multiple Hashes

Once completed, view your new file:

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The output will look like this:

[[See Video to Reveal this Text or Code Snippet]]

Handling Subdirectories

If your files are organized in several subfolders, running the command will automatically include them. The Get-ChildItem command can include all nested directories if you use the -Recurse parameter, like so:

[[See Video to Reveal this Text or Code Snippet]]

This command efficiently scans through all folders and subfolders, ensuring that every file's hash is captured.

Conclusion

By following the steps outlined in this guide, you've learned how to use PowerShell to export both SHA-256 and MD5 hashes of files in a directory into a CSV file. This simple yet powerful technique can help you maintain a high level of data integrity when working with client files, protecting you from unintentional tampering and errors. If you have any questions or need further assistance, feel free to ask!