Disk Image Hash Databases

TL;DR

Yes, several websites help you check if a disk image file is known (potentially malicious). These sites work by letting you submit the hash sum of your file – a unique fingerprint. They then compare it to databases of known good and bad images. Here’s how to use them effectively.

How to Check Disk Image Hashes

1. Understand Hash Sums: A hash sum (like MD5, SHA1, or SHA256) is a small string of characters that uniquely identifies a file. Even a tiny change in the file will result in a completely different hash sum.
2. Calculate the Hash Sum: You need to calculate the hash sum of your disk image *before* checking it against databases.
   • Windows: Use PowerShell:

     Get-FileHash -Algorithm SHA256 "C:pathtoyourimage.iso"

     This will output the hash sum. Replace C:pathtoyourimage.iso with the actual path to your file.

   • macOS/Linux: Use the command line:

     shasum -a 256 /path/to/your/image.iso

     Again, replace /path/to/your/image.iso with your file’s path.

3. Use Online Hash Databases: Here are some useful websites:
   • VirusTotal: https://www.virustotal.com/ – This is a very popular service that checks against many antivirus engines *and* allows you to submit file hashes directly.

     Go to the ‘Files’ tab and enter your hash sum.

   • Hybrid Analysis: https://www.hybrid-analysis.com/ – Similar to VirusTotal, but with a focus on more in-depth analysis.

     Use the ‘Search’ function and enter your hash sum.

   • NoVirusThankYou: https://www.novirusthankyou.org/ – Another good option for checking hashes against multiple antivirus engines.

     Enter your hash sum in the search box.

4. Interpret the Results:
   • Detected: If a database finds matches indicating malicious activity, *do not use* the disk image.
   • Not Found/Clean: A ‘not found’ result doesn’t guarantee safety – it just means the file hasn’t been submitted to that particular database yet. It’s still best to be cautious.

Important Considerations

• Hash Algorithm: Make sure you know which hash algorithm was used when creating the database entry (e.g., MD5, SHA1, SHA256). Using the wrong algorithm will give incorrect results. Most modern databases prefer SHA256.
• False Positives/Negatives: Hash databases aren’t perfect. False positives (incorrectly identifying a safe file as malicious) and false negatives (missing a malicious file) can occur.
• Privacy: Be aware that submitting files to online services may involve uploading the file itself or its hash sum, which could have privacy implications. Check the service’s privacy policy before submitting anything sensitive.