When using the Mole Ransomware Decryptor—originally developed by cybersecurity organizations like CERT Polska to combat the .mole extension malware—users frequently run into operational roadblocks.
The Top 5 common errors when running the Mole Decryptor and the step-by-step methods to fix them are outlined below.
1. Error: “Missing %TEMP% Database” / Initialization Failure
Why it happens: The decryptor relies heavily on the original database files and cryptographic markers left by the malware in the local Windows %TEMP% folder to reconstruct the decryption keys. If you ran a system cleaner before trying to decrypt, these files were likely wiped out. How to fix it:
Immediately disable automated maintenance software like CCleaner.
Use data recovery software (e.g., Recuva) to scan the C:\Users\Username\AppData\Local\Temp folder.
Restore any deleted temporary files or .tmp logs created on the day of the infection.
2. Error: “Access Denied” / “Failed to Write Decrypted File”
Why it happens: The decryptor lacks the elevated system permissions required to access, modify, or replace files in protected directories (such as Program Files or the root C: drive). How to fix it: Close the decryptor completely. Right-click the mole_decryptor.exe executable file. Select Run as Administrator from the context menu.
If files are on a network share, temporarily move a sample batch to a local folder like the Desktop to process them. 3. Error: “Invalid Key” or “Checksum Mismatch”
Why it happens: This occurs when you try to input a manual key retrieved from an online portal, but the key is corrupted or formatting characters (like spaces or trailing newlines) were accidentally included. It also happens if the file header itself was modified. How to fix it:
Open your key file or look at the key string provided by the portal. Copy it into a plain text editor like Notepad.
Strip away any accidental spaces at the beginning or end of the string.
Ensure you are using the correct command-line syntax if pasting the key directly into a terminal. 4. Error: “Unsupported File Version” / Partial Decryption
Why it happens: Ransomware operators constantly update their code. The original public Mole Decryptor was designed for early 2017 variants of the malware. If you are infected by a newer “Mole02” variant or a copycat strain, the cryptographic flaws used to build the tool may have been patched. How to fix it:
Do not overwrite your encrypted files; backup the encrypted versions first.
Check updated repositories like the No More Ransom Project to see if a newer version of the tool has dropped.
Reach out directly to CERT Polska via [email protected] with your log files, as they keep unreleased builds for variants that cannot be decrypted using the public tool. 5. Error: Decryptor Crashes or Loops Infinitely
Why it happens: The decryptor is choking on highly corrupted files, or an active antivirus program is mistakenly flagging the decryptor’s deep file-modifying behavior as a virus, halting its execution mid-process. How to fix it: Temporarily disconnect your PC from the internet.
Pause your antivirus software’s real-time protection strictly for the duration of the decryption process.
Run the decryptor on a single folder at a time rather than targeting the entire hard drive at once.
If you are still struggling to recover your files, let me know:
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