Breaking: .NSM Synology NAS Ransomware – File Recovery & Threat Analysis (2026)

Direct Answer: The .nsm ransomware (internally known as “Harrier” or “soc-sim”) specifically targets Synology NAS devices by exploiting exposed QuickConnect credentials. It utilizes partial XChaCha20 encryption. While a free, public decryptor is currently unavailable due to server-side key generation, recovery pathways are actively being developed through our advanced assessment service.

From the front lines of incident response, we know that an attack on your central storage infrastructure is paralyzing. Let’s cut through the noise. Our elite research team has been analyzing live .nsm samples and the attackers’ command-and-control (C2) infrastructure. We have identified critical structural flaws in how this Go-based malware encrypts files, specifically targeting the first 4096 bytes. Because the master keys reside on a highly restricted mTLS API server, a simple downloadable tool isn’t viable. Instead, we are handling these complex recoveries as a secure, managed service to ensure data integrity and prevent permanent loss.

Technical Identifiers for NSM / Harrier Ransomware

Identifier	Detail
Extension Name	.nsm, .hrr
Target Infrastructure	Synology NAS (via QuickConnect w/o 2FA)
Ransom Note Filename	READ_ME_UNLOCK_FILES.txt
Encryption Type	XChaCha20 (24-byte nonce) – Partial Encryption (First 4 KiB only)
Malware Binary	soc-sim-universal.run (Written in Go 1.26.4)
Attacker Contact	nasmids@tuta.com

What Does the Attacker Want? The Full Ransom Note Text

Transparency is critical. The attackers attempt to create a sense of urgency by setting strict payment deadlines and threatening data exfiltration. Below is the complete, verbatim ransom note dropped by this strain.

Plaintext

Hello, 
What Happened?
Your Network-Attached Storage (NAS) has been compromised.

What Does This Mean? Where Are My Files?
All your data has been encrypted and uploaded to our servers.

What Can I Do to Recover My Data?
If you want to recover your data, you need to send 0.07 BTC to the following address: 1AC27N1pfknqw1amhaQyaEvU77hLCRL1x9
Always double-check the address when copying and pasting it!

What Should I Do After I Send the Payment?
Your ID is: [Unique 64-character ID]
Please email us your ID and payment confirmation at: nasmids@tuta.com
Any messages other than payment confirmation will be ignored. Please respect your time and ours.
After we confirm your payment, you will receive detailed instructions on how to connect to our server and download all your data back. This process does not require any technical skills and is completed quickly.

Payment must be made by August 30th.

Can I Still Use My NAS?
Do not delete any files you find on your NAS.
Do not attempt to recover your data using any software, as this may result in permanent data loss.
Do not modify any volumes or storage pools on your NAS.
Do not write large amounts of data to your disk.

Why Have My Files Been Downloaded?
We reserve the right to leak or sell all your important documents if payment is not made.

They emphasize not attempting recovery with outside software. This is a standard scare tactic designed to protect their illicit revenue stream.

Immediate Actions: How to Contain a NAS Infection

Your NAS is likely still connected to the internet. Before considering data recovery, you must sever the attackers’ access to prevent further encryption or data theft.

1. Sever Network Connections: Immediately unplug the Ethernet cable from your Synology NAS. Do not simply turn off the device, as cutting power abruptly during disk operations can cause volume corruption.
2. Disable QuickConnect (Offline): Once network access is physically cut, log into your NAS interface via your local network. Navigate to Control Panel > External Access and completely disable QuickConnect.
3. Enforce 2FA: The primary entry vector for this attack is exposed credentials without Two-Factor Authentication. Mandate 2FA for all administrator accounts immediately.
4. Preserve Evidence: Do not delete the 54-byte footer attached to your encrypted files. This footer contains the original file extension and size, which is mathematically critical to the reversal process.

Our Professional Recovery Process Explained

Because the .nsm ransomware relies on an attacker-controlled API (/api/v1/recover) secured by mTLS client certificates, standard brute-force techniques fail. However, because the malware only encrypts the initial 4 KiB (4096 bytes) header of the file to maximize infection speed, the vast majority of your data remains structurally intact.

Our specialized incident response framework is engineered to exploit this specific vulnerability:

1. Secure Case Intake: Submit your READ_ME_UNLOCK_FILES.txt and a pair of files (one encrypted .nsm file and, if possible, its original unencrypted counterpart) through our secure portal.
2. Binary & Cryptographic Analysis: Our senior vulnerability researchers, including Aleksandar Petrovski and Dr. R. Yorgova, analyze the XChaCha20 implementation and the 24-byte nonce against known vulnerabilities in the Go soc-sim module.
3. Proof-of-Life Validation: We reconstruct the file header utilizing our proprietary derivation techniques and return a decrypted sample. Only upon your satisfaction do we move forward.
4. Bulk Decryption: We execute the decryption protocol across your isolated NAS volumes, ensuring the 54-byte footer is correctly parsed to restore original extensions without data loss.

Where to Go From Here

Ransomware targeting central storage requires a disciplined, calculated response. Report the incident to the FBI via IC3.gov, and do not communicate with nasmids@tuta.com. Engaging with the threat actors often marks you as a willing payer, increasing the likelihood of future attacks.

About the Author:

This threat intelligence advisory was produced by the security team at StopDjvuDecryptor.org. As a specialized ransomware research laboratory and division of Cloud Cover LLC—an Ohio-based Managed Service Provider—we deliver enterprise-grade incident response. Led by Lead Researcher Brent Kenreich, our mission is to provide victims with mathematically verified recovery alternatives to paying cybercriminals.

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