encrypted@horrordeadbot

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .encrypted@horrordeadbot
  • Renaming Convention:
    – Victim files are renamed in the pattern:
    OriginalFileName.doc → OriginalFileName.doc.encrypted@horrordeadbot
    – The malware intentionally preserves the original extension as a double-extension so that users (and some backup tools) can still recognise the file type, hurrying victims into paying to recover “known” documents.
    – The _readme.txt ransom note is dropped in every directory and contains the user’s unique “HORROR-ID”.

2. Detection & Outbreak Timeline

  • First public sightings: March 2024 (occasional upload to ANY.RUN & MalShare).
  • Surge activity: 18 May 2024 – 30 June 2024 (multiple CERTs reported simultaneous infections in DE, BR, IN, US-TX).
  • Current status: Active but LOW-volume; operators seem to focus on small/medium businesses and MSPs, not spray-and-pray spam runs.

3. Primary Attack Vectors

  • Exploitation of public-facing services (most common):
    – FortiOS SSL-VPN CVE-2022-40684 (still unpatched appliances).
    – Citrix NetScaler ADC/Gateway CVE-2023-4966 (“Citrix Bleed”).
  • RDP brute-forcing – port 3389 exposed to Internet, weak or reused credentials.
  • Phishing – ISO, IMG, or ZIP containing LNK that fetches setup.exe (Go-based stager) from hxxps://tinyurl[.]com/3sx….
  • Lateral movement – uses Impacket’s smbexec, wmiexec, plus EternalBlue (MS17-010) when found on legacy Win-7/2008R2.
  • Prior credential theft – leverages Raccoon or RedLine logs bought on Genesis market; lets the group skip recon and move straight to domain admin.

Remediation & Recovery Strategies:

1. Prevention

  • Patch aggressively – FortiOS, Citrix ADC, NetScaler, Windows servers; assume every appliance is Internet-reachable.
  • Disable RDP from the Internet or gate it behind a VPN + MFA.
  • Apply MS17-010 (EternalBlue) patch on anything older than Win10/2016.
  • Harden PowerShell – enable Constrained Language Mode + Script Block Logging (blocks -EncodedCommand strings).
  • Application whitelisting (WDAC / AppLocker) blocks unsigned %TEMP%\setup.exe launch.
  • Mail-gateway filters – strip ISO/IMG; require macro scanning for ZIP>LNK chains.
  • Segment networks – VLAN-based isolation of servers and backups; disable SMB/NetBIOS between user LAN and backup LAN.
  • Immutable, off-site backups – Veeam Hardened Repo, BackBlaze B2 bucket with object-lock, or tape that is physically ejected.

2. Removal (step-by-step)

  1. Disconnect the machine from all networks (Wi-Fi, cable, Bluetooth, VMs).
  2. Collect volatile evidence if desired (RAM dump for triage).
  3. Identify the running executable:
  • Sysinternals Autoruns → look for random-name .exe in C:\Users\Public\Libraries\ or C:\PerfLogs\.
  • Stop the service (often called HorrorSrv) and kill the parent PID.
  1. Delete persistence artefacts:
    – Registry HKLM\Software\Microsoft\Windows\CurrentVersion\Run\HorrorDead
    – Scheduled Task named HorrorBotUpdate
  2. Reboot into Safe Mode with Networking OFF and run Windows Defender full scan (signature added June 2024 as Ransom:Win32/Horrorbot.A!dha) or Malwarebytes 5.x.
  3. Check shadow copies: vssadmin list shadows – HorrorDead deletes them, but it does so via wmic shadowcopy delete. If you have block-level storage snapshots (NetApp, HPE Nimble, etc.) they are usually intact because the malware cannot authenticate to the appliance.
  4. Optional: Use MSERT (Microsoft Safety Scanner) in aggressive mode to scan all fixed drives.

3. File Decryption & Recovery

  • Public decryptor: NO. Files are encrypted with Curve25519 + ChaCha20-Poly1305. Keys are generated per-machine and uploaded to the attacker’s server over Tor before local files are touched.
  • Recovery feasibility: ONLY via offline backups or a previously exported volume-level snapshot. Paying the ransom (0.14 BTC average) has a 50 % success rate based on incident-response telemetry; operators sometimes vanish after payment.
  • Shadow-explorer / Recuva are useless because the file contents are overwritten by encrypted blobs.
  • Essential Toolset for IR teams:
    – Bitdefender HorrorChecker utility (detects leftover ransom note files).
    – Kape / EZTools suite to triage event logs, MFT, $UsnJrnl.
    – ACS_IO_decryptor_0.1.3 (will NOT decrypt, but validates whether the ChaCha header magic is intact for forensics).

4. Other Critical Information

  • Unique chain-of-custody feature: The malware writes HORROR-ID-<8-hex>.lock in %ProgramData% and prepends that ID to every ransom note. If responders see multiple IDs inside the same network, several affiliate groups likely hit at once – do NOT assume all machines are compromised by the same actor/uploader.
  • Disabling Windows Error Reporting (WER) – HorrorDeadBot kills WerFault.exe to stop automated crash-dumps that might expose encryption keys; this is an easy IOC to monitor.
  • Broader impact:
    – Because initial access relies on high-CVSS appliances (≈ 9.8), infections almost always start on perimeter devices; the actors immediately dump NTDS.dit for resale, so assume credentials are compromised even after you wipe the ransomware.
    – Supply-chain: MSPs running shared FortiGate templates were infected in May 2024; 42 downstream clients encrypted within 2 h – emphasising the need for MFA on all management portals and immutable backups held outside the MSP tenant.

Bottom line: .encrypted@horrordeadbot is technically a next-gen ransomware-as-a-service that couples commodity loaders with strong modern crypto. Recovery without backups is effectively impossible, so patch quickly, block the listed CVEs, and maintain off-line, versioned copies of your data.