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🦠 Malware Analysis
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Settra is a ransomware operation first identified in June 2026 that has already claimed 50-70+ enterprise victims across technology, manufacturing, financial services, healthcare, and retail sectors. The group operates double-extortion: data exfiltration followed by encryption and ransom negotiation via Tox and darknet portals.
🔹 Intrusion Methodology
Human-operated intrusions begin through compromised VPNs or valid accounts. Credential dumping uses Mimikatz and ProcDump. Lateral movement relies on dual-use tools including PAExec and NetExec. Durable remote access is established via Mesh Agent.
Before encryption, operators abuse signed STProcessMonitor drivers via BYOVD to blind endpoint defenses.
🔹 Encryptor Architecture
The encryptor is a two-stage design recovered through offline static reverse engineering by Cynet Research Labs.
Outer loader (win64.exe):
• Password-gated entry
• PEB export hashing for API resolution
• Anti-debugging gates
• ~200,000-round SHA-256 KDF for key derivation
• AES-256-CTR decryption of inner payload
• Custom LP77 decompression
• Process hollowing into a suspended self-copy
Inner PE payload executes systematic anti-forensics:
• Wipes 12 targeted event logs via wevtutil
• Purges Windows Prefetch
• Deletes PowerShell command history
• Wipes USN change journals
• Disables Windows Recovery (reagentc, bcdedit, wbadmin, Disable-ComputerRestore)
• Resizes VSS shadow storage stealthily
• Powers down Hyper-V VMs via WMI (ROOT\virtualization\v2) to release .vhdx file locks
🔹 Cryptography
Files encrypted using Windows CNG (BCryptGenRandom, BCryptEncrypt) with unique symmetric keys wrapped by an embedded 4096-bit RSA-1 public key. Files renamed to .locked (preceded by temporary .locked_wip). The RSA private key is never present on the victim host. The encryptor contains zero C2 network communication stacks, making it fully offline.
🔹 Detection Claims
Cynet claims proactive interception within 1 second of detonation via kernel-level driver decoy traps. This is a vendor claim from the same organization that performed the analysis, so treat with appropriate skepticism.
🔹 Key Takeaways
The encryptor design is notable for its complete lack of network communication, heavy anti-forensics targeting recovery infrastructure, and deliberate Hyper-V shutdown to access locked virtual disks. The BYOVD approach using signed STProcessMonitor drivers is increasingly common in ransomware operations.
🔹 ransomware
#malware #threatintelligence #BYOVD #reverseengineering
🔗 Source:
https://www.cynet.com/settra-ransomware-inside-a-new-enterprise-grade-extortion-threat/
