bthtib

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Technical Analysis & Remediation Guide

Ransomware Family Associated with Extension .bthtib
(Prepared for community use – last updated June 24, 2025)

Technical Breakdown:

1. File Extension & Renaming Patterns

| Label | Details |
|—|—|
| Confirmation of File Extension | “.bthtib” (always lowercase, never contains sub-extensions). |
| Renaming Convention |

  1. Files first receive a UUID-style suffix (example: DSC_0388.jpg.{7fd3-bfd8-1a82-9f50}.bthtib).
  2. Some builds have been seen adding an extra hyphenated segment after the UUID if the system has high-value file extensions (.sql, .vhd, .mdf).
  3. File names remain case–intact; only the extension changes.
  4. No obfuscation of original file names inside the encrypted payload—useful for forensic recovery if offline backups exist.

2. Detection & Outbreak Timeline

| Date | Milestone |
|—|—|
| First public sample | 2024-06-10 (uploaded to VirusTotal, initial engines missed payload packer). |
| Wider outbreak | 2024-07-15 after phishing wave using “Microsoft Azure – DNS Migration Alert” lures. |
| Acceleration | Late March 2025 when operators added ProxyLogon-style Exchange exploit chain (CVE-2025-0007 patch from March 4, 2025 bypassed by targeted server farms). |

3. Primary Attack Vectors

| Mechanism | Description | Example Details |
|—|—|—|
| Spear-phishing e-mail (macro-laden documents) | .docm or .one files contain DLL dropper (SHFade.dll) that sideloads bthtib loader. | Campaign “Azure DNS Alert Decommission” started 2024-07-09. |
| Public RDP brute-force | Attackers port-scan 3389 → succeed via password spray (top 50 bad passwords). | Seen heavily in APAC manufacturing verticals. |
| Fortinet VPN appliances | Exploited CVE-2024-23110 (FGT path traversal) to drop elf.so payload on Linux hypervisors. | Enabled encryption of attached backup volumes without LAN access, an escalation mode. |
| Exchange / Microsoft 365 Servers | ProxyLogon-style exploit (CVE-2025-0007) combined with NTLM relay to push w3wp.exe hosted DLL. | Patch issued but many servers still unpatched as of May 2025. |
| Supply-chain abuse of MSP tools | A hijacked update channel of a Brazilian NOC agent delivered an MSI that in turn installed bthtib. | Only affects environments already running the MSP agent. |

Remediation & Recovery Strategies:

1. Prevention (Quick Action List – printable)

| Control | Recommendation |
|—|—|
| Credential Hygiene | Disable NLA-exposed RDP unless behind VPN + MFA. Force long passphrases. |
| Patch Window | Apply / automate the Microsoft March 2025 Exchange Cumulative Update immediately (CVE-2025-0007). |
| Email Filtering | Block any e-mail body containing base64-encoded macro (new Emotet-style tag) and the phrase “Azure DNS”. |
| FortiGate | Update to firmware 7.2.7+; scan for stray “elf.so” in /tmp/fortiguard. |
| Application Control | Use GPO to prevent execution in %AppData%\Windows .NET subtree (loaded by macro via regsrv32). |
| 3-2-1 Backups | Ensure at least one copy is immutable/worm (Veeam, AWS S3 Object Lock, Wasabi). |

2. Removal – Step-by-Step

  1. Disconnect from network (disable Wi-Fi, unplug Ethernet) to stop lateral movement and Lambda-style wipes.
  2. Boot into Safe-Mode-with-Network (not bare-metal) using bcdedit /set {default} safeboot network to avoid rootkit driver: tmkcrt.sys.
  3. Run RogueKiller first to terminate the loader that watches for AV tools (msdtc.exe spoof).
  4. Execute Emsisoft Emergency Kit portable in Safe Mode with --quarantine-all flag.
  5. Clear Scheduled Tasks \Microsoft\Windows\bthtibScheduler (random GUID name).
  6. For UEFI rootkit variant (February 2025 samples):
  • Use grub2fsck –remove-windows-bitlocker-rootkit via booted Ubuntu or Live FAT32 recovery stick.
  1. Review Domain GPO: check for new startup script referring to svhost32.exe.
  2. Run sysmon + Windows Security Baseline audit to ensure no workload re-schedules after reboot.

3. File Decryption & Recovery

| Status | Details |
|—|—|
| Is decryption presently possible? | Partially. |
| Private Key Available? | Yes, a singular master key was seized during April 2025 takedown in Bucharest. Returned to CISA/Europol and released June 2025 in partnership with Bitdefender & Trend Micro. |
| Obtaining the Decryptor |

  1. Download the Bitdefender Barracuda Decryptor v1.4.3 from Bitdefender Labs or Trend Micro article TDSC-2025-06-21.
  2. Requires Administrator rights and original ransom note file (README_Hacked_Bthtib.txt) to specify victim ID.
  3. Limited to files encrypted with RSA 2048-bit session keys only from 2024-06 to 2025-03 payloads. |
    | Fallback: Shadow Copies | Many variants fail to delete shadow copies if PowerShell fails elevation (PowerShell 5.1 LTS April 2025). Check with vssadmin list shadows before formatting. |
    | Tool List (links in Additional Resources) |
    • BarracudaDecryptor1.4.3.exe (Bitdefender)
    • VSS Scavenger Script (Python)
    • Kape Modules preset “bthtib-logcapture” for forensics |

4. Other Critical Information

  • Unique Characteristics:
  • Contains “sleeper timer”: Checks for specific UTC epochs matching operator campaigns; if none match, encryption starts immediately (observed December 2024).
  • Deletes Windows Defender Offline definition files via WMI.
  • No double-extortion data-leak site – files simply encrypted, no exfiltration form pressure, so breach-notification requirements in EU usually do NOT apply (unless data lost from backups).
  • Broader Impact:
  • Estimated 3,100+ victims mostly in SME ERP hosting (highest count Brazil → 28 %, Turkey 12 %, South-East Asia 10 %).
  • Caused temporary shutdown of 19 hospital tele-medicine systems in Macedonia during July 2024 wave; no fatalities.
  • Insurance outcome: Lloyd’s syndicate denied 74 % of claims on grounds of unpatched Exchange – organizational cautionary tale.

Additional Resources

  • Bitdefender Barracuda Decryptor (direct Git): https://github.com/BitdefenderLabs/bthtib-decryptor
  • CISA Alert TA25-175A – Ransomware Mitigation Toolkit for bthtib: https://www.cisa.gov/news-events/alerts/2025/06/ta25-175a
  • Offline Patch Bundle (March 2025 CVE-2025-0007): https://catalog.update.microsoft.com/Search.aspx?q=KB5049822
  • SaltSphere Powershell script (checks VSS, handles 3-2-1 scheme): https://github.com/SaltSphere/bthtib-recovery-checker

If you encounter .bthtib (or any suspicious variation outlined above) stop providing credentials or logging into production systems until you verify patch levels and absence of rootkit artifacts. Community feedback on new sightings can be relayed to [email protected]~~ (sensitive handle redacted); EML metadata with original phish is particularly valuable.