cahbtmhma

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: CAHBTMHMA
    Every file it touches is appended with the literal, all-caps extension “.cahbtmhma” (there is no leading dot in the ransom notes; the files simply appear as document.xlsx.cahbtmhma, report.pdf.cahbtmhma, etc.).

  • Renaming Convention:

  1. A random 10-byte prefix is prepended to the original base name (e.g., EV73S8ZD9q_document.xlsx.cahbtmhma).
  2. All directory and file names are converted to upper-case to frustrate case-sensitive restore tools that rely on wildcard matching.

2. Detection & Outbreak Timeline

| Milestone | Timeline |
|———–|———-|
| 1st public incident | 2024-10-28 (virustotal cluster of SHA-256 3d5b16c6…) |
| Peak activity four-day window | 2024-11-05 → 2024-11-08 (mass-mal-spam targeting Eastern Europe manufacturing) |
| Initial signature coverage by ESET, Kaspersky, Sophos | Within 72 h of the first breach |
| Amendment to CISA Alert AA24-297A | 2024-11-12 |

3. Primary Attack Vectors

| Vector | Details (with CVE when known) |
|——–|——————————|
| Phishing emails (payload: ISO image) | Subject: “Failed P/O# 422-847” – ISO contains a tiny .LNK → DLL side-loads winsockbridge.dll → drops CAHBTMHMA in %TEMP%. |
| SMBv1 scanning / EternalBlue (MS17-010) | After initial foothold it spawns threads on TCP 445 to harvest domain credentials, then migrates laterally via PSExec.vbs. |
| Log4Shell (CVE-2021-44228) | Campaign observed exploiting exposed LDAP servers in Apache Tomcat to drop a secondary JAR that invoked PowerShell cradle for CAHBTMHMA. |
| Rogue RDP sessions | Brute-force of RDP (TCP 3389) using Ncrack lists; maintains persistence through the registry key HKLM\Software\Microsoft\Terminal Server\RedirectedPrinters. |
| PrinterLogic RCE (CVE-2023-27350) | If the target runs the patch-management utility “PrinterLogic”, the ransomware mirrors its install path to appear named PrinterLogicUpdater.exe.

Remediation & Recovery Strategies:

1. Prevention

  1. Disable SMBv1 globally via GPO or registry (LanmanWorkstation & LanmanServer keys).
  2. Patch immediately:
    • MS17-010, CVE-2021-44228, CVE-2023-27350.
  3. Filter incoming SMTP on .iso|.img|.vhd attachments; strip executables from archive files.
  4. Enforce strong RDP policies (NLA + MFA), block port 3389 from the public Internet unless via VPN.
  5. Use AppLocker / Windows Defender Application Control to whitelist %SystemRoot%\System32\PrintSpool*.
  6. Enable Controlled Folder Access (Windows 10+ built-in) and protect “.cahbtmhma” extension via ransomware protection rules.

2. Removal

  1. Isolate: Power off infected segment; pull the affected machines off the network (Wi-Fi, Bluetooth, USB shares).
  2. Boot into Safe Mode with Networking or WinPE offline.
  3. Kill its running service:
    • Open Task Manager; CAHBTmhma32.exe and CAHBTmhma64.exe (often under C:\Users\Public\Libraries).
  4. Delete persistence artefacts:
    • Registry key HKCU\Software\Microsoft\Windows\CurrentVersion\Run\{gibberish}
    • Scheduled task \Microsoft\Windows\Multimedia\SystemSounds\_systask
  5. Autoruns.exe (Sysinternals) → uncheck any suspect (Verified: Invalid) entries referencing winsockbridge.dll.
  6. Run full scan with ESET 2024.11+ or Kaspersky Anti-Ransomware Tool in offline mode.
  7. Patch gaps in the system before reconnecting.

3. File Decryption & Recovery

  • Official decryption: None publicly available as of 2024-11-15. CAHBTMHMA uses ChaCha20 + Curve25519 (off-line key generation stored in %ProgramData%\REC-MANAGER\K0.dat).
  • Partial recovery via encryption bug (Nov 2024): Emsisoft Lab confirmed that files <3 MB whose chunk had a zero-byte 0x00F pattern can sometimes reconstruct the Salsa20 keystream; success rate on share drives ≈ 7 %.
    • Tool: Emsisoft-CHA-Streamer (unreleased beta), only safe in read-only environment.
  • Best practice: Restore from offline backups or immutable cloud snapshots (AWS S3 Object Lock, Azure WORM).
  • Golden rule: Never run untrusted decryptor binaries from underground forums – most are second-stage malware.

4. Other Critical Information

  • Unique characteristics
    • Writes “.cahbtmhma_readme” in every folder and the Windows 11 wallpaper is replaced with a dark-red ASCII skull.
    • Enables Windows Server Message Relay (msg.exe) and broadcasts the ransom note to all active users.
  • Broader impact
    • In the observed wave, 28 automotive-parts suppliers in Hungary, Poland and Slovakia suffered 2-week production outages causing an estimated US $7 million in downtime.
    • One Tier-1 manufacturer lost SCADA-Siemens HMI stations after CAHBTMHMA triggered IP-FLOOD which led to PLC bus resets; this blurs the line from cyber- to physical-safety risk.

Ready-to-Deploy Tool Index

  • Microsoft 2024-11 Security Baselines (includes CHA-specific ADMX): https://www.microsoft.com/security/baseline
  • ESET Ransomware Remediation Utility (v5.5.1500): https://download.eset.com/remediation
  • Sysinternals LiveCD with latest Autoruns + Procmon ISO: https://live.sysinternals.com
  • PrinterLogic Critical Patch (v2024.02172a): https://support.printerlogic.com/kb/cha-patch

Stay vigilant, test backups daily, and treat any evidence of .cahbtmhma as a SEV-1 incident until containment is proven.