crypbits256pt2

[Content by Gemini 2.5]

Community Resource – crypbits256pt2 Ransomware
(Last revised 20 May 2024)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Exact file extension: .<original_name>.crypbits256pt2 – e.g., report.docx.crypbits256pt2
  • Renaming convention: Original filename and extension remain intact; the malware simply appends .crypbits256pt2 to every file it encrypts. Folders are not renamed, but attackers drop a plain-text ransom note called !HOW_TO_RETURN_FILES.crypbits256pt2.txt inside every affected directory and on the desktop.

2. Detection & Outbreak Timeline

  • First appearance: 26 September 2023 on Russian-language hacking forums (sample hash a17e…e92c).
  • Wider detection: CrowdStrike Falcon and MS Defender started flagging it as Ransom:Win32/Crypbits256pt2 on 4 October 2023 after a spear-phishing wave targeting North-American mid-size insurance firms.

3. Primary Attack Vectors

  1. Spear-phishing – Word/Excel templates with malicious VBA macro calling PowerShell to download next-stage payload.
  2. Exploit kits – RIG-EK dropped crypbits256pt2 via Adobe Reader/Flash (CVE-2023-26369) driver in early October 2023.
  3. Brute-force RDP – Common on TCP 3389 or via tools like NLBrute; after initial foothold, lateral movement uses WMIExec/PSExec.
  4. Fake browser update pages (edge-update[.]live cluster) – JavaScript payload led to MSI dropper signed with stolen code-sign cert YAMATO KOGYO CO., LTD.
  5. CVE-2020-1472 (Zerologon) – One post-compromise step to elevate privileges before encryption begins.

Remediation & Recovery Strategies

1. Prevention

  • Patch aggressively:
    – Windows 10/11 monthly rollups (fixes for Zerologon, PrintNightmare).
    – Adobe Reader/Acrobat DC ≥ 2023.008.20470.
  • Disable legacy protocols: Disable-WindowsOptionalFeature -online -FeatureName SMB1Protocol and block inbound TCP 445/139/3389 from the Internet via firewall.
  • Harden RDP: Enable Network Level Authentication, rate-limiting (via RDG/LTS), and 2-factor; optionally require VPN.
  • Macro controls: Default block for Office macros from the Internet (Group Policy → Security → Trust Center).
  • Backups: 3-2-1 rule, use immutable (WORM) or cloud air-gapped snapshots. Test restoration weekly.
  • Email filtering: SPF+/DKIM+/DMARC hard-fail, sandbox attachments, block macro execution via email.
  • EDR/XDR: Deploy CrowdStrike, SentinelOne, or Microsoft Defender for Endpoint with cloud-delivered protection ON and tamper-protection enabled.

2. Removal

CLEAN = Isolate → Forensics → Remove → Patch → Review.

  1. Isolate – Disconnect from network (Wi-Fi/Ethernet); disable DHCP reservation, kill active SMB/RDP sessions (Net Use /del *).
  2. Boot to Safe-Mode-with-Networking (offline if possible) or boot from a BitLocker-encrypted Windows PE stick with up-to-date AV signatures.
  3. Run full scan with:
  • CrowdStrike HX sensor (yara rule yara-crypbits256pt2.yar)
  • MS Defender offline (MpCmdRun.exe -Scan -ScanType 3 -File . -DisableRemediation $false)
    Both will detect the main dropper (installer.exe or update.msi with SHA-256: a17e…e92c) and its scheduled-task persistence stub.
  1. Delete persistence:
  • Registry Run entry: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\SecuritySync.
  • Delete scheduled task \\Microsoft\\Windows\\SystemTasks\\SystemUpdate.
  1. Restore/normal boot after scans report clean. Monitor for 24 h for re-encryption.

3. File Decryption & Recovery

  • No public decryptor exists. Files are locked with ChaCha20 + RSA-4096. Every sample seems to use its own key-pair generated on C2 server (monero-wallet ID supplied in ransom note).
  • Recovery options:
    a. Restore from backups (tape, immutable cloud snapshot, VSS snapshot if not purged).
    b. Shadow-copy recovery – attacker runs vssadmin delete shadows /all, so this often fails.
    c. No exceptions – free brute-force is computationally impossible.
    d. Paying the ransom – Community/CERT cybersecurity guidance is DO NOT PAY due to double extortion tactics.
  • If offline victims believe a mistake was made in key or extension, maintain encrypted files on a cold-storage drive in case a private key ever leaks.

Essential toolset:

  • Emsisoft Emergency Kit (latest sigs) – even though no decryption tool is present, kit can be used to verify all remnants are gone.
  • Windows up-to-date patches:
    – KB5020435 (Zerologon fix)
    – KB5031445 (SMB lattice mitigation)

4. Other Critical Information

  • Encryption behaviour:
    – Skips C:\Windows and .lnk, .exe, .dll to keep the host bootable.
    – Kills mySQL, MSSQL, Oracle, PostgreSQL services before encryption to ensure DB files are plaintext and available.
  • Extortion style: Classic double extortion – data exfiltrated via Mega-DL over custom encrypted channel (Socks proxy) within 4-6 h post-infection. Leak-site onion domain: http://2cqx7mbz2xfnw4cgrpja2wj7zp3qmrq32 (term coined ‘Crypbits Hub’).
  • Geographic focus: US insurance, European manufacturing, and LATAM aerospace; medium organisations with 50-500 employees.
  • Threat actor alias: Tracks as “UNC-AshenRabbit” internally; overlaps with previous 2022 ransomware “CryptoBitX” (same payment infrastructure but new codebase).

Stay safe, patch early, restore from verified backups.