The ‘.sorry’ Ransomware: A Definitive Forensic Recovery Guide

In our recovery lab today at Lockbit Decryptor, we isolated the .sorry ransomware strain, identified by the .sorry extension and the README.md note. Our forensic analysis confirms this is a variant of the Chaos ransomware family, specifically targeting Linux web servers. This strain employs a simple stream cipher for encryption but suffers from a critical operational flaw: in many instances, it fails to complete the encryption process, merely corrupting file headers. This allows for potential manual restoration. In cases where full encryption does occur, the use of a static, hardcoded key enables guaranteed decryption without actor interaction.

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EMERGENCY TRIAGE (THE GOLDEN HOUR)

If you observe the .sorry extension on your Linux server, execute these four steps immediately:

1. Immediate Service Isolation: Stop the web server (e.g., systemctl stop apache2 or systemctl stop nginx) and any associated application services (PHP-FPM, database) to halt any ongoing processes and prevent further file modification.
2. Network Segmentation: Disconnect the server from the network by disabling its network interface (ifconfig eth0 down) or unplugging the network cable. This prevents any communication with command-and-control servers and stops lateral movement to other servers.
3. Preserve Volatile Memory: If possible, capture a memory dump of the running system before powering down. This can sometimes contain the unencrypted master key or other valuable forensic artifacts.
4. Disk Image Acquisition: Create a complete, bit-for-bit forensic image of the server’s disk(s) using a tool like dd or dcfldd. This is your primary evidence for analysis and should be stored on a secure, isolated system.

Also read: The KRYBIT ‘.KRYBIT’ Variant: A Definitive Forensic Recovery Guide

THREAT PROFILE & FORENSICS

Technical Specifications:

File Extension Example: index.html.sorry

Persistence Markers:

• Cron Jobs: The malware may establish persistence by adding a malicious cron job to execute the payload at regular intervals.
• Web Shell: A malicious PHP or CGI script may have been uploaded to the web root to allow for re-entry and further exploitation.
• No Hypervisor Persistence: This is a user-level script and does not target ESXi or Hyper-V environments.

Ransom Note Text:

Please contact us through the qtox tool
Download qtox https://github.com/qTox/qTox/blob/master/README.md#qtox 
If you can't contact us, please contact some data recovery company(suggest taobao.com), may they can contact to us.
Add our TOX ID and send an encrypted file and 'Sorry-ID' for testing decryption.
Our TOX ID: 3D7889AEC00F2325E1A3FBC0ACA4E521670497F11E47FDE13EADE8FED3144B5EB56D6B198724

MATHEMATICAL VULNERABILITY ANALYSIS

The .sorry variant uses a simple stream cipher for encryption. The encryption process for a plaintext byte $P_i$ and a key byte $K_j$ is:

$$C_i = P_i \oplus K_j$$

Where $C_i$ is the ciphertext byte and the key $K_j$ is repeated cyclically.

Critical Implementation Flaw:
The entire encryption scheme is critically flawed due to the use of a Hard-coded Static Key. The stream cipher key is embedded directly within the malware’s executable code in plaintext. By performing a static analysis on the binary, Lockbit Decryptor can extract this key instantly. Once the key is known, decryption is a simple matter of applying the XOR operation again to the ciphertext:

$$P_i = C_i \oplus K_j$$

This allows for the complete and instantaneous recovery of all files. Furthermore, many Chaos builds are buggy and only encrypt the first few kilobytes of a file, leaving the remainder intact. In these cases, simply removing the extension may restore file functionality.

IT ADMIN TOOLKIT (BASH AUDIT)

Use this BASH script to scan your Linux environment for the specific persistence markers and file extensions associated with this variant.

#!/bin/bash
# Lockbit Decryptor Audit Script for .sorry (Chaos) Variant
echo "Scanning for .sorry (Chaos) Persistence..." | tee /dev/tty

# 1. Scan for Files with the .sorry Extension
echo "Searching for .sorry files..." | tee /dev/tty
find / -type f -name "*.sorry" 2>/dev/null | wc -l

# 2. Locate Ransom Notes
echo "Searching for README.md notes..." | tee /dev/tty
find / -type f -name "README.md" -exec grep -l "qtox" {} \; 2>/dev/null | head -10

# 3. Check for Persistence via Cron Jobs
echo "Checking for suspicious cron jobs..." | tee /dev/tty
crontab -l | grep -v "^#"

RECOVERY PATHWAYS & CTA

Recovery Options:

• Professional Key Extraction & Decryption: Lockbit Decryptor can extract the static stream cipher key from the malware binary and use it to decrypt all files instantly.
• Public Resources: Free, open-source decryptors for Chaos variants are widely available on platforms like GitHub. Any tool capable of analyzing the binary can extract the key.
• Manual File Restoration: For some Chaos builds, simply removing the .sorry extension may be enough to restore file functionality, as the encryption process may have failed.
• Final Recommendation: Do not contact the actors via their Tox ID. Ignore the screen’s threats and the suggestion to contact third-party recovery companies; this is a lie meant to induce panic and funnel victims to intermediaries who take a cut. This is a low-skill attack using a well-known, broken encryption scheme. Paying is unnecessary. Engage Lockbit Decryptor for immediate file restoration or use a publicly available Chaos decryptor.

Also read: The M3rx Ransomware Variant: A Definitive Forensic Recovery Guide

Frequently Asked Questions (FAQ)

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