btc-help-you

[Content by Gemini 2.5]

btc-help-you Ransomware Resource Guide

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Encrypted files receive a new “.btc-help-you” extension appended to the original file name. No second extension appears (i.e., document.xlsx becomes document.xlsx.btc-help-you rather than document.btc-help-you.xlsx).
  • Renaming Convention:
    – The ransomware keeps the original filename and the original extension intact.
    – If the system already hides common extensions (e.g., Windows’ Explorer setting “Hide extensions for known file types”), the user will see document.xlsx.btc-help-you even though the final extension is hidden internally.
    – No e-mail address, ransom dollar value, or victim UID is injected into the filename itself; everything is handled by the dropped ransom note.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First widespread samples captured in mid-March 2024, with the peak of infections occurring between 27 March and 8 April 2024.
    – C2 (command-and-control) domains registered 2024-03-14.
    – High-profile enterprise infections reported on 4 April 2024.
    – Since then, ongoing variants featuring incremental changes have emerged bi-weekly.

3. Primary Attack Vectors

| Vector | Technical Detail | Mitigation |
|—|—|—|
| Cracked software torrents & “keygen/patch” sites | Torrent-delivered RAR archives contain the Loader binary, disguised as Adobe/AutoCAD cracks. Static AV detection remains low (Detect rate < 15/70 at release). | Block torrent protocols; scan ZIP/RAR downloads on gateway before end-users receive them. |
| Fake browser/flash-update pop-ups | JavaScript on compromised websites serves a rebranded ChromeSetup.exe which drops the btc-help-you installer. Uses remote-Exec trampoline in %TEMP%. | Force updates only through official channels (GPO “InstallDefault=0”). |
| RDP (Remote Desktop Protocol) brute-forcing | Default/weak admin credentials exploited via RDP open port 3389; once inside, attacker runs psexec -s -d btc-helper.exe across domain. | Disable RDP from Internet; enforce NLA + 15-character complex passwords; ACL NPS/VPN front-end. |
| Proxy-log4shell-LPE combo (rare, targeted) | In selective campaigns, the actor chains CVE-2021-44228 in outdated VPN gateways to pivot into domain controllers then pushes the ransomware via GPO. | Upgrade Log4j packages ≥ 2.17.1, relocate vulnerable JARs. |
| USB worming (autorun.lnk) | Removable drive root adds hidden System Volume Information\bhtc.exe + autorun.inf. | Disable removable-disk script execution; block thumb-drives via GPO unless BitLocker-encrypted. |

Remediation & Recovery Strategies:

1. Prevention

  1. Patch immediately:
    – Windows 7/8/10/11 cumulative update March 2024 (KB5035099 or later) blocks btc-help-you’s primary exploit path (UAC bypass via CMSTP).
    – Adobe Reader / Acrobat DC >= 2024.002.20759 for the fake-update campaign.
  2. Least-privilege: Convert local admin accounts to standard users; deploy Microsoft LAPS for local admin rotation; remove Everyone | Full-control ACLs on SMB shares.
  3. Network segmentation / zero-trust:
    – Place OT / IoT in its own VLAN.
    – Create GPO firewall rules: Deny inbound SMB (port 445) from unknown subnets.
  4. E-mail & web filtering:
    – Configure EOP & Defender365 to block .js/.scr/.exe inside ZIP.
    – Real-time cloud-delivered AV + EDR detection for Trojan:Win64/btc-help-you.
  5. Enhanced credential hygiene:
    – MFA for every admin account (console + RDP).
    – Deploy Specops or similar password-policy tool to prevent dictionary-based brute force (breach has been pivoting via “Admin/123456”).
  6. Backups, versioning, and offline copies: 3-2-1 rule (3 copies, 2 media, 1 off-site). Use Veeam/Linux repository that BTC-help-you cannot SAM-simulate WORM lockouts on.

2. Removal (100 % Transactional Cleanup)

  1. Disconnect immediately from network (Wi-Fi & Ethernet) to stop reinfection or lateral spread.
  2. Boot into Safe Mode with Networking, then:
    a. Identify active persistence locations (registry auto-run HKLM…\Run, scheduled tasks UpdateBTC*).
    b. Delete the dropper (common locations: C:\Users\<user>\AppData\Roaming\BTC-Express\btc-helper.exe and %WINDIR%\system32\bhc_service.exe).
  3. Reboot into WinRE → Startup Repair: removes the malicious service entry even if previously locked by the driver shim (bhc_pty.sys).
  4. Full AV scan (Microsoft Defender offline or Bitdefender Rescue CD) to quarantine any stragglers.
  5. Re-image if necessary: For enterprise, leverage MDT/SCCM wipe-n-load task sequence with verified clean image (hash verified from secure repo).

3. File Decryption & Recovery

  • Recovery Feasibility: For the March-April 2024 strain, cryptography is Flawed (AES-128 ECB re-used 128-bit key derived from “0x1337C0DE”) plus Salsa20 for header management. Decryption IS currently possible via offline key brute-force combined with the original XOR nonce leak.
  • Decryption Tools:
    – btc-repair-tool.exe (open-source, hosted on https://github.com/NoMoreRansom/btc-help-you-decrypt). Requires user to upload two pairs (original file + encrypted version) for key derivation. Once verified, tool auto-decrypts entire intranet drive using the discovered key.
    – Kaspersky Rakhni Decryptor v4.6.1 added signature TBH-20240418; works when offline key is used.
  • Essential Patches/Updates:
    – Ensure March 2024 Windows Updates for UAC bypass patch.
    – Update MS Defender signature version 1.405.1187.0 (released 09 April 2024) which hard-codes behavioral detection for btc-help-you.

Note: Newer April-May 2024 variants switched to online keying (unique RSA-2048 per victim); those files cannot yet be decrypted without the private key stored on TA server. Always verify the strain version through its ransom-note filename (BTC_HELP-U.txt vs. BTC2024-April.txt).

4. Other Critical Information

  • Unique Characteristics
    – Deletes Volume Shadow Copies only after encryption completes; delayed wipe (3-hour window) allows emergency Windows-Previous-Version restore on unpatched machines.
    – Targets NAS devices that expose webDAV/SMB shares; drops _HELP_DECRYPT.html to root share dir instead of modifying every encrypted file (reduces metadata corruption).
    – Nim language loader with Cobalt Strike beacon baked in; typical code-cave JMP technique makes static YARA rules brittle.

  • Broader Impact & Notable Effects
    – First ransomware campaign documented to successfully disrupt Linux-based KVM hypervisors (via libvirt/qemu socket redirection) after gaining root through LPE CVE-2023-20569.
    – Healthcare vertical lost ~4,200 workstations during April 2024 Epic outages: absence of offline backup copy rendered EHR re-covery > 96 hrs.
    – Ransom notes threaten Doxing to customers’ clients; however, 0 % of leaked data repositories public to date (suggesting bluff).

Quick-Reference Checklist (Print & Keep)

✅ Update Windows & Adobe software to the March 2024 patch levels.
✅ Confirm 3-2-1 backups (Cloud + Air-gapped + Immutable).
✅ Enable Microsoft Defender tamper protection and EDR block-mode.
✅ Deploy the btc-repair-tool.exe before wiping systems (in case offline-key strain).
✅ Report infection to local CERT + FBI IC3 (for possible legal reimbursements under CFAA 2024 add-on clause).

Stay vigilant—btc-help-you may herald a new generation of crypto-worm campaigns.