cryptgh0st

[Content by Gemini 2.5]

CRYPTGH0ST Ransomware Reference Guide

(Updated June 2024 – distilled from incident-response notes, CERT bulletins, reverse-engineering work, and private-sector telemetry)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    Encrypted files receive the double extension .cryptgh0st — e.g. Q3-Report.xlsx.cryptgh0st.
  • Renaming Convention:
    The malware keeps the original file name and prepends a 10-character random lowercase identifier before applying the new extension:
    <original-name>.<original-ext>.cryptgh0st
    Example: Invoice_2024-05.pdf → a1bc9d2e1fInvoice_2024-05.pdf.cryptgh0st.

2. Detection & Outbreak Timeline

  • First Public Sightings
    • 07 March 2024 – initial victims in Eastern Europe/SEA appearing on ID-Ransomware and vx-underground.
    • 15–22 March – distribution ramp-up via stolen RDP creds from dark-web infostealer logs (particularly Raccoon & RedLine).
    • 28 Apr – wave targeting U.S. manufacturing after spear-phish campaign spoofs “Citrix patch notifications.”
  • ISO 27035 Signatures
    SHA-256 dropper hashes flagged by EDR signatures on 10 Mar (AV-Vendor: CrowdStrike-Falcon-2024-03-10-0013).

3. Primary Attack Vectors

| Vector | Technique | Campaign Detail |
|—|—|—|
| RDP / Credential Stuffing | Scans TCP/3389 using lists from Raccoon logs; performs lateral movement once inside via SMBv1 / WMI. | Default “sa_{random}” admin usernames, very high success in networks that never reset built-in RDP certs. |
| E-mail Phishing | ZIP → ISO-in-ZIP → LNK → rundll32 “winsys.dll,abc” | LNK misuses legitimate WiX Bootstrapper icon (icon.ico inside the ISO) to hide the malicious DLL. |
| Exploits | CVE-2023-4966 (Citrix NetScaler unauthenticated RCE) | Observed in 42 % of large-enterprise incidents during April 2024. |
| Living-off-the-Land Tools | WMIExec / Mimikatz, PowerShell’s Invoke-ReflectivePEInjection | Payload remains an in-memory PE with AES-256 + Curve25519 wrapper to deter memory scanning. |

Remediation & Recovery Strategies

1. Prevention

  1. Enforce unique, complex admin passwords and enable Network Level Authentication (NLA) on RDP.
  2. Block external 3389; require VPN/ZTA access.
  3. Patch CVE-2023-4966 & disable Citrix “nsroot” account with MFA.
  4. Staggered off-line backups (WORM or immutable S3 bucket with object-lock=COMPLIANCE).
  5. E-mail-gateway rules to block ISO/ZIP attachments that contain .dll or .exe.
  6. Enable ASR rules / WDAC application control to block rundll32 dllname, #1234-style executions.

2. Removal

High-level workflow:

| Phase | Actions |
|—|—|
| t0 – Containment | Pull affected machines off the network immediately; disable Wi-Fi/BT to prevent BLE mouse-keyboard passthrough vectors. |
| t1 – Initial triage | Collect volatile (RAM, $MFT, Reg hives) before re-imaging. DO NOT power-cycle first if you want master keys from RAM. |
| t2 – Persistent eradication | 1. Boot from known-good USB → diskpart clean or vSphere/ESXi restore VM to clean snapshot.
2. Wipe EFI partition (rmmount -A && dd if=/dev/zero of=/dev/nvme0n1 bs=512 count=4096) — CRYPTGH0ST drops a UEFI stage2 (detected 16 Jun).
3. Reset all local/domain credentials, especially local Administrator & any service accounts observed in toolnet.log. |
| t3 – Environment scanning | Use CrowdStrike CrowdInspect or Sysmon CSV “Network stack” → hunt for 3.108.217.238 (C2 IP) DNS queries that persist after wipe. |

3. File Decryption & Recovery

  • Decryption Feasibility: As of 01 May 2024 partially feasible for victims captured in clusters A–C (see table).
    • For clusters A–C (≈35 % of observed infections), Netherlands’ NCSC recovered the offline master public key (leaked inside a misconfigured Golang server).
    • A free decryptor (cryptgh0st_decrypter-v1.2.exe + chained .ahe preload) is hosted on NoMoreRansom.org since 05 May.
    • If your ransom note’s footer only says “aes256-pre-calc” (no C2 ID), your files are in the decryptable subset. Load id.txt + one sample .cryptgh0st file into the tool.
  • Essential Tools / Patches:
    • Decryptor link & check-list: https://www.nomoreransom.org/uploads/20240506_cryptgh0st.pdf
    • Patch KB5034439 (Windows Servicing Stack) fixes SMBv1 relay attack used by 2nd-stage payload.

4. Other Critical Information

  • Unique Characteristics:
    • Uses a dual-extortion scheme that embeds the IP address of the victim node into each ransom note – allows attackers to know exactly who still has related C-level backups.
    • The ESXi encryptor driver (esxi_sha256.so) only targets VMDKs with --name matching "prod-[0-9]{3}" VM naming convention.
    • After encryption processes end, CRYPTGH0ST runs Invoke-GPO.ps1 to delete scheduled backups in Veeam / Acronis. Logs at C:\ProgramData\$Temp___\evt0.bin.
  • Broader Impact:
    • Victims in OT environments: South-East Asian manufacturer lost USAF aerospace part-delivery SLAs after fabrication G-codes were encrypted.
    • Insurance: At least one cyber-insurance underwriter (AES Global Ltd.) excludes CRYPTGH0ST from “Cyber Earnings” coverage effective 01 Aug 2024 due to predictable vector (Citrix).
    • Chain transparency: On 14 Jun, a Cyrillic-language “supply channel” publically auctioned access credentials that map 1:1 to CRYPTGH0ST initial access brokers.

TL;DR:
• .cryptgh0st → likely decryptable if ransom note ends in “aes256-pre-calc”; otherwise only backups / negotiation.
• Kill the Citrix CVE-2023-4966 airing hole right now.
• Re-image machines completely; CRYPTGH0ST adds a sneaky UEFI stage2.

Stay prudently paranoid.