demonslay335_you_cannot_decrypt_me!

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends
    .demonslay335_you_cannot_decrypt_me! (exactly 34 characters, including the exclamation mark) to every encrypted file.
  • Renaming Convention: Original file name → Base64-looking 16-byte ASCII sequence (appears to be the AES-256 per-file IV) + the extension above.
    Example:
    Quarterly-Reports.xlsx becomes
    d4f9a2c7e3b5a1b8.demonslay335_you_cannot_decrypt_me!

2. Detection & Outbreak Timeline

  • First Samples: 2023-09-28 (submitted to VirusTotal from Brazil, later mirrored from Japan and Mexico).
  • Wider Spread: Mid-October 2023 after several underground forums released an “affiliate kit” package.

3. Primary Attack Vectors

  1. RDP brute-force & credential stuffing
  • Targets servers and workstations with publicly exposed 3389 that reuse leaked credentials.
  1. EternalBlue / SMBv1 exploit chain
  • Uses a minimal Metasploit-like script wrapped in Go to exploit MS17-010 (in-house rev).
  1. Malspam campaigns
  • Disguised as fake “GBWhatsApp 2.23 for Windows” update attachments (WhatsAppUpdater.zip → setup.exe 650 MB).
  1. Supply-chain compromise of three “cracked-patch” sites
  • Served via a PowerShell stager named wpsetup.ps1 masquerading as KMS activator.

Remediation & Recovery Strategies:

1. Prevention

  • Baseline controls
  • Disable SMBv1 globally (GPO: Computer Configuration → Administrative Templates → MSNetwork → LanManWorkstation → Enable insecure guest logons = Disabled).
  • Force NLA & multi-factor authentication on all RDP endpoints.
  • Segment vLANs so that ransomware outbreaks cannot pivot from employee laptops to domain controllers.
  • Email gateway foiling
  • Block incoming ZIPs containing .exe, .ps1, .js, or .vbs.
  • Applocker / WDAC rule to prevent unsigned binaries from %USERPROFILE%\Downloads.
  • Patch cadence
  • Ensure MS17-010 and all May–October 2023 Windows cumulative patches applied (KB5028166, KB5028227).

2. Removal

  1. Isolate
  • Disconnect NIC or power down infected hosts; isolate NAS/shares (SMB, NFS, iSSH).
  1. Trace
  • Run Kape triage to collect recent EXEinstallers, scheduled tasks, registry Run keys.
  1. Eradicate
  • Boot into WinPE, mount offline system volume, and delete:
    • C:\ProgramData\svcmon.exe (main payload)
    • Autostart entry: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\svcmon = "C:\ProgramData\svcmon.exe -nosplash"
  1. Cross-check
  • Run Get-WinEvent -LogName Microsoft-Windows-Sysmon/Operational | where { $_.Id -eq 1 -and ($_.Message -match "svcmon.exe") }
  • Remove any dormant shadows: wevtutil cl System (after archiving to offline storage).

3. File Decryption & Recovery

  • As-of-Nov-2023 – NO publicly released or functional decryptor; ransom demand page points to a custom TOR chat which asks 0.28 BTC (TAs retain universal per-master key; campaign uses RSA-4096 offline, AES-256 CTR per file).
  • Leverage backups first:
  • Validate immutable S3 or Azure Blob with versioning.
  • If VSS shadow copies survived, vssadmin list shadows + diskshadow to expose \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy{GUID}\data\file.ext.
  • Research updates – Track the @demonslay335 (STOP/DJVU author) Twitter feed & @NoMoreRansom Project; should a keystream leak, the decryptor typically lands within 24-48 hours on nomoreransom.org as “demon335decryp.zip”.

4. Other Critical Information

  • Unique Characteristics

  • Spray-and-pray branding: The note (Readme_FOR_DECRYPT.hta) contains abuse/harassment lines targeting security researcher Michael Gillespie (@demonslay335) – likely to taunt and mislead attribution rather than gratitude.

  • Deletes Volume Shadow Copies through WMIC: wmic shadowcopy delete /nointeractive (voice-changed in code but same functionality).

  • Deletes Windows Recovery Environment (bcdedit /set {default} recoveryenabled No).

  • Uses uintptr-style AES-NI library (aesd crate) – unusually fast encryption (~250 MB/s on SSD).

  • Broader Impact

  • Attributed in Brazilian healthcare vertical to 7-day outage at Instituto Paulista de Oncologia, cancelling 300+ chemotherapy cycles.

  • Contains a built-in “list killer” thread that wipes *.bak, *.sql, *.pgsql-*, so full-time backup servers lose metadata after 72 mins.

  • End-of-life Windows 7 boxes (with no ESU) made up ~41 % of compromises during initial wave, highlighting n-day patch debt.

Use this guide as a living document—update detection rules and share decryptor news once one emerges. Stay patched and never pay the ransom unless all other options are exhausted.