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Introduction:
A single PDF-themed shortcut—masquerading as a harmless document—now serves as the entry point for one of the most modular and destructive malware frameworks ever observed. Dubbed Avalon, this newly discovered threat actor toolkit combines credential theft, lateral movement, remote access, and the CrownX ransomware payload into a single, AI-assisted attack chain that bypasses traditional security controls with alarming efficiency. By the time the ransom note appears, the damage is already done: credentials are stolen, C2 communications are established, and every local recovery option has been systematically destroyed.
Learning Objectives:
- Understand the complete multi-stage attack chain—from a Proton Drive-hosted ISO to full CrownX ransomware deployment.
- Identify the specific defense evasion techniques used, including ETW tampering and MSBuild abuse.
- Learn actionable detection and mitigation strategies, including command-line hunting and EDR hardening.
- The Attack Chain: From PDF LNK to Ransomware Execution
The Avalon framework is distributed through a sophisticated, multi-stage phishing campaign that begins with a spoofed legal document email. The email directs recipients to a password-protected archive hosted on Proton Drive—a legitimate cloud storage service that often bypasses email security gateways.
Step-by-step breakdown:
- Initial Lure: The victim receives an email that appears to be a legal document, guiding them to a Proton Drive link. The archive contains an ISO image, which is used instead of a directly attached malicious file to evade email-layer detection.
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The .LNK Shortcut: Inside the mounted ISO image, the victim finds a file named “Secure Document CA-283505.pdf.lnk”—a Windows shortcut that appears to be a PDF document. Double-clicking this shortcut triggers the next stage.
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MSBuild Execution: The .LNK file runs a command that launches MSBuild.exe, a legitimate Windows .NET build tool, to execute an MSBuild project file embedded within the ISO. This is a classic “Living Off the Land” (LOLBin) technique that allows the attacker to run malicious code without dropping a traditional executable file.
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.NET Assembly & ETW Tampering: The MSBuild project loads an embedded .NET assembly. This assembly immediately interferes with Event Tracing for Windows (ETW), a core Windows logging subsystem, to drastically reduce forensic visibility. By tampering with
EtwEventWrite(), the malware hides its activity from security logs and EDR telemetry. -
HTTPS Payload Download: With ETW effectively blinded, the malware downloads the next-stage payload over HTTPS from a remote server. This payload deploys the full Avalon framework, which then proceeds to harvest credentials, move laterally, and ultimately deploy the CrownX ransomware.
Detection Commands (Windows):
To hunt for suspicious MSBuild activity and ETW tampering, security teams can use the following commands:
Check for MSBuild execution with unusual command-line arguments
Get-WinEvent -LogName "Microsoft-Windows-Sysmon/Operational" | Where-Object { $<em>.Message -like "MSBuild.exe" -and $</em>.Message -like ".xml" }
Monitor for ETW tampering attempts (Event ID 11 for process creation with suspicious parent)
Get-WinEvent -LogName "Security" | Where-Object { $<em>.Id -eq 4688 -and $</em>.Message -like "EtwEventWrite" }
Search for ISO mount events
Get-WinEvent -LogName "Microsoft-Windows-Kernel-General/Operational" | Where-Object { $<em>.Id -eq 1 -and $</em>.Message -like ".iso" }
2. Defense Evasion: How Avalon Stays Invisible
Avalon’s defense evasion subsystem is its most dangerous feature. The framework is specifically designed to conceal its execution from Microsoft Defender, SentinelOne, CrowdStrike, Sophos, Elastic Endpoint, FortiEDR, ESET, McAfee, and Bitdefender.
Key evasion techniques:
- ETW Patching: By tampering with Event Tracing for Windows, Avalon prevents security tools from receiving critical telemetry data. This is often achieved by patching the `EtwEventWrite` function in memory, causing all ETW events to be silently dropped.
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User-Mode Monitoring Bypass: The framework uses multiple methods to reduce telemetry and bypass user-mode monitoring, adjusting its execution based on the specific defensive controls present on the host.
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Anti-Forensic Cleanup: After completing its objectives, Avalon removes traces of its artifacts to complicate incident response efforts. This includes deleting temporary files, clearing event logs, and overwriting critical forensic evidence.
Linux Equivalent (for cross-platform awareness):
While Avalon targets Windows, understanding similar evasion techniques on Linux is valuable:
Monitor for tampering with auditing subsystems (auditd)
sudo auditctl -l | grep -i "exclude"
Check for suspicious ptrace usage (often used for process injection)
sudo grep "ptrace" /var/log/syslog
Monitor for deletion of audit logs
sudo find /var/log -1ame ".log" -mtime -1 -exec ls -la {} \;
Mitigation Strategy:
- Enable Sysmon with comprehensive logging to capture process creation, network connections, and file creation events.
- Configure Windows Defender Application Control (WDAC) to restrict which applications can execute MSBuild.exe.
- Deploy Endpoint Detection and Response (EDR) solutions that can detect ETW patching through memory scanning and behavioral analysis.
3. CrownX Ransomware: Encryption, Extortion, and Recovery Disruption
CrownX is the final extortion stage of the Avalon framework, but its impact extends far beyond file encryption. The ransomware is designed to maximize damage while minimizing the victim’s ability to recover.
Core Capabilities:
- File Encryption: CrownX encrypts files associated with business operations, software development, engineering, data storage, and virtual infrastructure using the Windows Cryptography API (CryptoAPI).
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Ransom Note & Payment: The malware delivers a ransom note containing payment instructions and deadline timers that show how much time is left before the ransom amount is increased.
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Recovery Destruction: CrownX terminates the Volume Shadow Copy Service (VSS) and deletes all shadow copies, effectively eliminating the most common Windows recovery mechanism.
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Disk-Level Damage: The framework directly interacts with disk structures, likely in an effort to damage partition information, boot records, or other critical areas of the drive—rendering the system completely unusable.
Windows Commands to Check VSS Status and Shadow Copies:
Check VSS service status sc query VSS List existing shadow copies vssadmin list shadows Delete all shadow copies (if needed in a controlled recovery scenario) vssadmin delete shadows /all /quiet Check disk partition structure diskpart list disk list volume
Detection of CrownX Activity:
Look for suspicious CryptoAPI usage
Get-WinEvent -LogName "Microsoft-Windows-CryptoAPI/Operational" | Where-Object { $<em>.Id -eq 7 -or $</em>.Id -eq 8 }
Monitor for VSS deletion attempts
Get-WinEvent -LogName "System" | Where-Object { $<em>.Id -eq 7036 -and $</em>.Message -like "Volume Shadow Copy" }
Hunt for known CrownX file extensions (if discovered)
Get-ChildItem -Path C:\ -Recurse -ErrorAction SilentlyContinue | Where-Object { $_.Extension -match ".crownx|.encrypted" }
4. Credential Harvesting and Lateral Movement
Avalon is not just a ransomware dropper—it is a comprehensive post-exploitation framework that systematically compromises the entire network.
Data Targeted for Theft:
- Browsers: Credentials, cookies, history, and bookmarks from Chromium-based browsers and Mozilla Firefox.
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Cryptocurrency Wallets: MetaMask, Phantom, Coinbase Wallet, Exodus, Electrum, Atomic Wallet, Ledger Live, and Bitcoin Core.
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Communication Apps: Discord, Slack, and Microsoft Teams.
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VPN & Network: OpenVPN, WireGuard, and Windows Credential Manager.
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System Information: SSH known hosts, saved RDP connections, Wi-Fi profiles, and Group Policy Preferences (GPP) cpassword artifacts.
Exfiltration and C2 Communication:
All stolen data is exfiltrated to a remote server (helloxcherry[.]com), which also serves as a command-and-control (C2) hub for receiving tasking commands. The framework performs reconnaissance to prioritize systems that can expand the scope of the compromise.
Network Detection Commands:
Monitor for outbound connections to suspicious domains
Get-1etTCPConnection -State Established | Where-Object { $_.RemoteAddress -match "helloxcherry|proton" }
Check DNS cache for suspicious entries
ipconfig /displaydns | findstr "helloxcherry"
Monitor for credential dumping (LSASS access)
Get-WinEvent -LogName "Security" | Where-Object { $<em>.Id -eq 4656 -and $</em>.Message -like "lsass.exe" }
Linux Command to Monitor for Similar Activity (network-based):
Monitor for suspicious outbound connections sudo netstat -tunap | grep ESTABLISHED | grep -v "192.168|10.0|172.16" Check for unusual DNS queries sudo tcpdump -i any -1 port 53 -v
5. AI-Assisted Development: The New Threat Landscape
One of the most concerning aspects of Avalon is that it shows signs of artificial intelligence (AI)-assisted development. The framework assembles multiple sophisticated components with scant regard for traditional tradecraft or operational security, something that would normally require significant expertise to build.
Implications:
- Lowered Barrier to Entry: AI lowers the barrier to entry, making malware development more accessible with little time and effort.
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Increased Threat Volume: Even actors with limited technical expertise and resources can now produce tools that previously required extensive development effort.
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Rapid Evolution: The modular design of Avalon means that its capabilities can be updated or extended after initial deployment, making it highly adaptable and persistent.
Defensive Recommendations:
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Behavioral Detection: Move beyond signature-based detection to behavioral analysis that identifies malicious patterns regardless of the code used.
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AI-Powered Defense: Deploy AI-driven security tools that can detect anomalies and adapt to new threats in real-time.
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Zero Trust Architecture: Implement a Zero Trust model that assumes compromise and verifies every access request, regardless of origin.
What Undercode Say:
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The Attack is Over Before the Ransom Note Appears: By the time CrownX encrypts your files, Avalon has already stolen your credentials, established C2 communications, and destroyed your backups. The ransom note is just the final insult.
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Traditional Email Security is Not Enough: The use of Proton Drive, ISO images, and legitimate Windows tools like MSBuild allows Avalon to bypass traditional email gateways and endpoint protection. Organizations must adopt multi-layered defenses that include user awareness training, application whitelisting, and advanced EDR.
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ETW Tampering is a Critical Blind Spot: Event Tracing for Windows is a fundamental logging mechanism that many security tools rely on. Attackers are increasingly targeting ETW to blind defenders. Organizations should deploy tools that can detect ETW patching and implement redundant logging mechanisms.
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AI is Democratizing Cybercrime: The AI-assisted development of Avalon is a wake-up call. Cybercriminals are leveraging AI to build sophisticated malware faster and cheaper than ever before. Defenders must similarly adopt AI to keep pace.
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Recovery Disruption is the New Normal: Avalon’s ability to destroy shadow copies, damage disk structures, and disable backup processes represents a shift in ransomware tactics. Organizations must adopt the 3-2-1 backup strategy (3 copies, 2 different media, 1 offsite) and regularly test their recovery procedures.
Prediction:
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-1 The democratization of AI-assisted malware development will lead to a surge in sophisticated, multi-stage attacks like Avalon. Organizations that fail to adopt AI-driven defenses will be increasingly vulnerable.
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-1 ETW tampering will become a standard feature in advanced malware, forcing Microsoft and EDR vendors to implement new detection and mitigation techniques. The cat-and-mouse game between attackers and defenders will intensify.
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+1 The disclosure of Avalon’s attack chain will prompt security vendors to improve their detection capabilities, particularly around MSBuild abuse, ISO mounting, and ETW patching.
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-1 Small and medium-sized businesses (SMBs) will be disproportionately affected, as they often lack the resources to deploy advanced EDR and security awareness training.
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+1 The incident will accelerate the adoption of Zero Trust architectures and application whitelisting, as organizations realize that traditional perimeter defenses are no longer sufficient.
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-1 The use of legitimate cloud services like Proton Drive for malware delivery will force cloud providers to implement more rigorous content scanning and abuse detection mechanisms, but attackers will continue to find new ways to abuse trusted platforms.
▶️ Related Video (82% Match):
https://www.youtube.com/watch?v=8JsA40mmCFM
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