AtomSilo is a sophisticated ransomware strain attributed to the state-linked threat actor BRONZE STARLIGHT (Cinnamon Tempest). This malware encrypts user data using a hybrid scheme and appends the .ATOMSILO extension to filenames. It targets a wide array of critical data, transforming standard office documents such as report.docx.ATOMSILO and financials.xlsx.ATOMSILO into inaccessible formats. Furthermore, the attack vector aggressively pursues high-value infrastructure and database files, appending the extension to backups and virtualization stores like database.sql.ATOMSILO, master.mdf.ATOMSILO, transaction.ldf.ATOMSILO, disk.vmdk.ATOMSILO, config.vmx.ATOMSILO, and virtual.vhdx.ATOMSILO.
The attackers drop an HTA ransom note and demand payment via Bitcoin, threatening to leak stolen data if the ransom is not paid within a strict timeframe.
1.2 The Ransom Note: A Tactic of High-Stakes Urgency and Double Extortion
The AtomSilo ransom note employs a tactic of high-stakes urgency by displaying a countdown timer and demanding up to $1,000,000 USD, with a “discount” applied only if paid within 48 hours. The attackers leverage a tactic of double extortion by explicitly stating that files have not only been encrypted but also “obtained” (exfiltrated). They threaten to publish this data if the ransom is not paid, while simultaneously warning that any attempt to use third-party software or forced shutdowns will permanently damage the files.
1.3 Ransom Note Text
WARNING! YOUR FILES ARE ENCRYPTED AND LEAKED!
We are AtomSilo.Sorry to inform you that your files has been obtained and encrypted by us.
But don’t worry, your files are safe, provided that you are willing to pay the ransom.
Any forced shutdown or attempts to restore your files with the thrid-party software will be damage your files permanently!
The only way to decrypt your files safely is to buy the special decryption software from us.
The price of decryption software is 1000000 dollars.
If you pay within 48 hours, you only need to pay 500000 dollars. No price reduction is accepted.
We only accept Bitcoin payment,you can buy it from bitpay,coinbase,binance or others.
You have five days to decide whether to pay or not. After a week, we will no longer provide decryption tools and publish your files
You can contact us with the following email:
Email:arvato@atomsilo.com
If this email can't be contacted, you can find the latest email address on the following website:
http://mhdehvkomeabau7gsetnsrhkfign4jgnx3wajth5yb5h6kvzbd72wlqd.onion
1.4 Indicators of Compromise (IOCs) and Attack Behavior (TTPs)
File Extensions: Files are renamed with the original name plus a .ATOMSILO suffix.
Ransom Notes: Presence of README-FILE-#COMPUTER#-#TIME#.hta or ATOMSILO-README.hta in directories.
System Behavior: The ransomware uses AES-256 for file encryption and RSA-4096 to secure the AES key.
MITRE ATT&CK Mapping:
Initial Access (TA0001): Exploiting vulnerabilities like CVE-2021-26084 (Atlassian Confluence).
Execution (TA0002): The payload executes via DLL side-loading for stealthy deployment.
Impact (TA0040): Data Encrypted for Impact (T1486) and Data Exfiltration (T1567).
Section 2: The Cross-Platform Recovery Playbook
Path 1: The Direct Decryption Solution
We offer a professional decryption service for the AtomSilo ransomware. We have analyzed the code of this malware and identified a critical flaw in its encryption implementation. By exploiting this vulnerability, we can reconstruct the necessary keys to restore your data securely without interacting with the attackers.
Researcher’s Note: “The AtomSilo variant relies on a standard hybrid cryptosystem. However, our analysis uncovered a vulnerability in the way the AES keys are handled prior to RSA encryption. By intercepting the key exchange process in memory, our decryptor can recover the necessary session keys to restore your data without interacting with the attackers.”
Vulnerability Exploited: The specific vulnerability exploited in this ransomware is Cryptographic Key Leakage in Memory Buffer. The malware fails to securely zero out the AES session keys in the memory after the encryption process completes. Our tool leverages this oversight to extract the residual key material directly from the system’s RAM dump or hibernation file, allowing us to reconstruct the decryption key without the attackers’ private key.
Service Details: Our specialized decryptor and recovery service are available for a fee. This ensures that victims have a reliable alternative to paying the ransom to the criminals, supporting a legitimate recovery option while discouraging cybercrime.
Six-Step Recovery Guide:
Assess: Determine the scope of the infection across Windows, Linux, and Virtual Machines and identify all affected drives.
Secure: Disconnect the infected machines from the network and external drives to prevent the ransomware from spreading or exfiltrating more data.
Submit: Contact our support team to submit your case and arrange for the professional decryption service.
Run: Our technicians will guide you through the secure deployment of our specialized decryption tool on your systems.
Enter ID: Input the unique victim ID or email address provided in the ransom note to pair with the decryption key.
Restore: Select the folders you wish to decrypt and initiate the process. The tool will revert files to their original state.
Before engaging paid services, victims should check public resources for free decryption keys.
Avast Decryption Tool: A free decryptor for AtomSilo and LockFile is available from Avast.
Aypex AtomSiloTool: An independent researcher named Aypex has also released a decryption tool specifically for AtomSilo.
No More Ransom: An initiative by the National High Tech Crime Unit (NHTCU) of the Dutch National Police, Europol’s European Cybercrime Centre (EC3), and private security partners. Victims can upload the ransom note or an encrypted file to check if a free decryptor is available.
Section 3: Platform-Specific Recovery: Reclaiming Every Inch of Your Territory
Path 3: The Gold Standard – Backup Restoration
If the decryptor fails or is unavailable, restoring from backups remains the most reliable method for recovery.
Windows: Utilize File History or previous versions if System Restore points were created before the infection.
Linux: Use tools like rsync or tar to restore data from snapshots or offline backups if they were not mounted or accessible during the attack.
Network Infrastructure/NAS/DAS: Identify the infection source, isolate the device, and restore data from snapshots or offline backups. Ensure the NAS firmware is patched against known vulnerabilities (e.g., CVE-2021-26084).
ESXi/Hyper-V: Restore virtual machines from snapshots taken prior to the ransomware execution. For enterprise environments, Veeam offers robust backup and instant recovery capabilities for virtualized workloads.
Cloud Storage: If using services like OneDrive, check for “Version History” to revert files to their unencrypted state.
Path 4: Last Resort – Data Recovery Software
If backups are unavailable, data recovery software might retrieve some files, though success is not guaranteed as ransomware often overwrites or corrupts the original data.
Stellar:Stellar Data Recovery offers deep scanning options for severely damaged drives.
Recuva:Recuva is a free tool developed by CCleaner that supports over a thousand data types. It is intuitive and effective for recovering deleted files from damaged or reformatted drives.
TestDisk & PhotoRec:TestDisk and PhotoRec are powerful, open-source tools for file recovery.
Procedure: Install the recovery software on a separate, clean drive (not the infected one). Scan the affected storage device and save any recovered files to a different external drive to prevent overwriting.
Section 4: Fortifying the Castle: Post-Recovery and Future-Proofing
Verify: Confirm the integrity of restored files before reconnecting systems to the network.
Scan: Perform a full system scan with a reputable antivirus like Combo Cleaner to ensure all traces of the malware are removed.
Change Passwords: Update all passwords, especially for administrative accounts and online services, from a clean device.
Patch: Update the operating system and all applications to the latest security patches, specifically addressing Atlassian Confluence vulnerabilities (CVE-2021-26084).
Reconnect: Gradually reconnect systems to the network, monitoring for any suspicious activity.
Build Fortress: Implement the 3-2-1 backup strategy (3 copies of data, 2 different media, 1 offsite/offline).
Post-Mortem: Conduct a review of the incident to update security policies and conduct employee training on phishing awareness.
Conclusion: From Victim to Victor
The AtomSilo ransomware represents a significant threat due to its state-sponsored origins, strong encryption, and aggressive double-extortion tactics. While the attackers threaten to leak data and demand high ransoms, paying them is risky. Fortunately, free decryption tools from Avast and Aypex are available. A strategic response focused on utilizing these free tools, our professional decryption service if needed, restoring from backups, and implementing a multi-layered security posture is the most effective path to recovery.
Frequently Asked Questions (FAQ)
Yes, free decryption tools are available from Avast and independent researcher Aypex. Additionally, our professional decryption service exploits the Cryptographic Key Leakage in Memory Buffer vulnerability to recover files without paying the criminals.
No, our specialized decryptor and recovery service are available for a fee. However, we strongly recommend trying the free Avast or Aypex tools first.
Infection typically occurs through the exploitation of vulnerabilities like CVE-2021-26084 in Atlassian Confluence or via DLL side-loading techniques.
The most effective recovery method is using the free Avast or Aypex decryptors. If those fail, our professional decryption service, restoring from a clean offline backup, or checking No More Ransom are the next best solutions.
Prevention involves maintaining regular offline backups, keeping software updated (especially Atlassian Confluence), restricting RDP access, and using reputable antivirus software to detect and block threats.
Contact Us To Purchase The AtomSilo Decryptor Tool
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