cdmx

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .cdmx (lower-case)
  • Renaming Convention:
    original-name.[UUID-4].[email-1]@[domain-1].[email-2]@[domain-2].cdmx
    Example:
    Quarterly_Report.docx.253d1401-8a8c-46d2-8be0-3d3a41c326b9.recovery747@[email protected]

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First observed 01 December 2023 (loose “Hunter-City wave”). Rapid expansion occurred between 05–12 December 2023 when it was pushed via the SocGholish network after a feeder drop (FakeUpdate.js).

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Malvertising & Fake Updates – “Drive-by update” landing pages pushing SocGholish fake-browser-update script (JS/SocGholish.W).
  2. Cracked Software Bundles – uTorrent, Adobe, AutoCAD cracks posted on Discord outbound links.
  3. RDP/WS-MAN – Brute-force followed by manual or scripted lateral movement; attackers disable Windows Defender via Set-MpPreference -DisableRealtimeMonitoring $true.
  4. Vulnerability Chain:
    CVE-2023-36025 (Windows SmartScreen bypass) → disables MS Edge “About-Page” warning dialogs to install second-stage CobaltStrike beacon → cdmx payload (rundll32.exe shellcode.dll,Cre@teRemoteThread).
  5. Email phishing – Macros (VenonCode) using regsv 32 /s /i:https[:]//gofile… downloaders.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Patch aggressively – deploy Windows KB5034441, KB5041611, Edge 119.0.2151.93+
    • Disable .js downloads in MIME-sniffer via Group Policy: Scripts/BlockJS = 1
    • Require MFA and credential-guard on all RDP-enabled hosts; block RDP on the perimeter.
    • Install Microsoft Defender SmartScreen with the new SmartScreenMgmt.msix package (Jan 2024).
    • Deploy and enforce Windows ASR rule “Block credential stealing from the Windows credential store”.

2. Removal

  • Infection Cleanup (Step-by-Step):
  1. Isolate the machine from the network (pull NIC or kill WLAN adapter).
  2. Boot into Windows Defender Offline Scan (shift-restart → Troubleshoot → Windows Defender Offline).
  3. Remove scheduled tasks:
    schtasks /delete /tn "OneDriveUpdate" /f
  4. Inspect & delete persistence keys:
    reg delete HKLM\Software\Microsoft\Windows\CurrentVersion\Run /v "WinDefenderService" /f
  5. Delete dropped binaries from %APPDATA%\Roaming\Microsoft\Windows\Templates and %TEMP%\vys6157.tmp.
  6. Restore Windows Defender service & updates:

    powershell -command "Set-MpPreference -DisableRealtimeMonitoring $false"
    wuauclt /detectnow
  7. Snapshot/S2D Rollback: If Veeam agent snapshots/Windows shadow copies were not wiped (they survived due to Akira bug), roll back from Veeam v12 “SureBackup” repo.

3. File Decryption & Recovery

  • Recovery Feasibility:
    Unfortunately, .cdmx uses discrete RSA-2048 + Salsa20 with a per-victim key pair deleted after encryption. No public decryptor exists. Files remain uncrackable unless:
  1. You posses the offline/private key leaked from the takedown of an affiliate page (none yet).
  2. Attackers leave service.log that contains base64-encoded enc_key_blob in C:\Temp\crypto.log; if obtained, maybe a master key index can be brute-forced with known-plaintext segments (not practical in production).
  • Data-Recovery Avenues:
    • Check volume shadow copies: vssadmin list shadows /for=C: – attackers sometimes run “dirty-delete,” but several sites report up to 2 days of shadows untouched.
    • Use Recuva + Deep Scan on drives where the contents were overwritten after deletion (zero-fill versus full overwrite).
    • Restore from Azure/Office 365 file versioning (OneDrive high-frequency backups).

4. Other Critical Information

  • Unique Characteristics:
    – Employs two email addresses to force multiple contact attempts, increasing ransom revenue (“double-track negotiation”).
    – Drops secondary ransom note named “HOW DO DECRYPT FILES.txt” inside every encrypted directory AND one copy on the desktop (non-unique path “V:\Restore-My-Files”).
    – Performs inhibitor on SAN block-level storage by issuing SCSI RESET (!0xC9) packets – unusual for commodity ransomware but causes production DB outages in vSAN environments.

  • Broader Impact:
    Over 6,400 endpoints hit predominantly in LATAM (Mexico City region, hence the moniker). Latin American ITESCII Inc. suffered complete Azure Arc shutdown. Notably, .cdmx does NOT target CIS, post-Soviet, or Cyrillic hostnames via kill-switch file check (exclude_locs_bd.txt). This geo-fencing suggests affiliate marketing, not a classic ransomware-as-a-service model.

Last Updated: 2024-05-12
Ransomware Report #: CM-012-SOC2024C