Avast Decryptor for HermeticRansom: Free Tool, Compatibility, and InstructionsAvast’s decryptor for HermeticRansom is a free utility released to help victims of the HermeticRansom (also known as HermeticWiper/Hermes variants in some reports) ransomware family recover files without paying the attackers — when recovery is possible. This article explains what the decryptor can and cannot do, which systems and file types it supports, how to prepare for and run the tool, troubleshooting tips, and safer next steps after recovery.
What is HermeticRansom?
HermeticRansom refers to a family of ransomware that encrypts files on infected systems and demands payment for a decryption key. Variants may differ in encryption algorithms, key management, and victim-targeting methods. In some incidents, the malware used high-quality cryptography; in others, mistakes by developers allowed security vendors to produce working decryptors.
Key fact: Avast provides a free decryptor when a recoverable flaw or leaked key is available.
When can the Avast decryptor help?
The Avast decryptor is useful under these conditions:
- The particular HermeticRansom sample affecting the system is one for which Avast has identified a weakness or obtained keys.
- The victim has retained the encrypted files and any related artefacts (like ransom notes, encrypted file samples, or the original encrypted filenames and extensions).
- The system was not completely wiped or further damaged by post‑infection actions (for example, reinstallation without backups may make recovery impossible).
It will not help when the ransomware uses strong, uncompromised asymmetric encryption with per-victim keys that are not available to researchers.
Key fact: The decryptor only works for specific HermeticRansom variants that Avast can decrypt — not for every ransomware labeled “Hermetic.”
Compatibility and supported platforms
Avast’s decryptor is typically released as a Windows executable, because HermeticRansom primarily targets Windows environments. Compatibility details depend on the specific decryptor release:
- Operating systems: Windows 7, 8, 8.1, 10, 11 (32- or 64-bit support depends on the particular tool).
- File systems: NTFS and FAT variants are commonly supported where files remain intact.
- File types: The decryptor targets file formats encrypted by the ransomware; common user documents, images, archives, databases, and other files may be supported if the ransomware encrypted them in a recoverable way.
Always consult the decryptor’s readme or Avast’s release page for exact system requirements and supported file lists.
Before you begin — safety and preparation
- Isolate the infected machine:
- Disconnect it from the internet and any local networks to prevent further spread.
- Do not pay the ransom:
- Paying funds attackers do not guarantee recovery and funds criminal activity.
- Make a forensic copy:
- If possible, make a sector-level image of the affected drive before attempting recovery or running any tools. This preserves the original state for further analysis.
- Collect information:
- Save ransom notes, encrypted filenames and extensions, and sample encrypted files. Note the ransom demand messages and any attacker contact addresses.
- Scan for remaining malware:
- Use up-to-date antivirus/anti-malware tools (on a separate clean system if needed) to detect and remove the ransomware components before attempting decryption.
- Back up encrypted files:
- Copy encrypted files to an external drive; never overwrite originals until you are sure the decryptor works.
Key fact: Always image the drive and back up encrypted files before running any decryptor.
How to use Avast Decryptor for HermeticRansom — step-by-step
Note: these are general steps. Follow the specific README included with the decryptor you download from Avast for exact commands and options.
- Download the decryptor:
- Obtain the official decryptor from Avast’s website or their official support/download page. Do not download decryptors from unverified third-party sites.
- Verify integrity:
- If Avast provides a checksum or digital signature, verify the downloaded file to ensure it hasn’t been tampered with.
- Prepare the environment:
- Work from a clean Windows system, preferably booted into Safe Mode or a recovery environment if recommended by Avast.
- Remove active threats:
- Run a full malware scan and remove ransomware executables. If removal modifies encrypted files, use the original backup copies.
- Place encrypted files in one folder:
- For convenience, copy encrypted files into a directory on a local drive or external storage.
- Run the decryptor as administrator:
- Right-click the executable and choose “Run as administrator” if required. Many decryptors need elevated privileges to access file locations.
- Select target folder(s):
- Use the decryptor’s interface to point to the folder(s) containing encrypted files.
- Start decryption:
- Initiate the process and monitor progress. Decryption speed depends on file count and size.
- Verify recovered files:
- Check a representative sample of files to ensure they open correctly. Do not delete encrypted copies until you confirm successful recovery.
- Post-recovery checks:
- Reboot and run full security scans; apply OS and software updates; change passwords and review logs to confirm the system is clean.
Common issues and troubleshooting
- Decryptor reports “unsupported variant”:
- Ensure you are using the correct decryptor release. Check file extensions and ransom note text; Avast’s documentation often lists identifying markers.
- Decryption fails for some files:
- Corruption may have occurred. Try other backups or previous versions (Volume Shadow Copies) if available.
- Tool won’t run:
- Run as administrator, disable conflicting security tools temporarily, and ensure Windows version compatibility.
- False positives or interference:
- Antivirus or endpoint protection may block the decryptor executable. Temporarily allow or whitelist the tool while you run it.
What if Avast’s tool doesn’t work?
If the Avast decryptor cannot recover your files:
- Consult other reputable decryptor repositories (for example, national CERTs or other major AV vendors) to see if alternative tools exist for that variant.
- Check whether backups exist (cloud backups, network shares, external drives).
- Consider professional incident response or data recovery services — especially for business-critical systems.
- Preserve evidence and device images for potential law enforcement assistance.
Key fact: Not all ransomware infections are decryptable; backups remain the most reliable recovery method.
Prevention and hardening after recovery
- Maintain regular, tested backups using the 3-2-1 rule (3 copies, 2 different media, 1 offsite).
- Keep OS and applications patched and minimize exposed services.
- Use reputable endpoint protection with behavior-based detection.
- Enforce least privilege and multi-factor authentication.
- Train staff to spot phishing and social-engineering attempts.
Legal and ethical notes
- Do not attempt to use or distribute decryptors on systems you do not own or have explicit permission to access.
- In some jurisdictions, interacting with attacker infrastructure or paying ransoms may have legal implications. Consult legal counsel and law enforcement when necessary.
Final checklist (quick)
- Isolate infected machine — yes/no
- Image the drive — yes/no
- Back up encrypted files — yes/no
- Download official Avast decryptor — yes/no
- Run decryptor as admin and verify recovered files — yes/no
- Update, patch, and harden systems — yes/no
If you want, provide one encrypted file sample name/extension and the ransom note text (do not paste sensitive personal data) and I can help identify whether Avast’s decryptor release might match your case.
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