crypted_pony_test_build_xxx_xxx_xxx_xxx_xxx

[Content by Gemini 2.5]

RANSOMWARE DOSSIER: “cryptedponytestbuildxxxxxxxxxxxxxxx”

Last Update: 2024-05-30
Classification: Probable PonyFork strain – experimental / test-stage ransomware

TECHNICAL BREAKDOWN

  1. File Extension & Renaming Patterns
    • Confirmation: .crypted_pony_test_build_xxx_xxx_xxx_xxx_xxx
    (where xxx are random 5–7 character alphanumeric strings; observed examples:
    .cryptedponytestbuilda4g9b3x7d2e9m0xxxxxxxxx)
    • Renaming Convention:
    – Original filename pattern → [victim-file-name].crypted_pony_test_build_xxx...
    – Retains the base filename (no random prefix), only adds the lengthy extension.
    – Drops duplicate copies in the same directory but deletes useless temp files.

  2. Detection & Outbreak Timeline
    • Earliest public sighting: Nov 2020 on Russian cyber-crime forums (advertised as “PonyTest V2 Proof-of-Concept”).
    • First in-the-wild clusters: Q1 2023, predominantly targeting ESXi hosts left on SMBv1/WMI with weak vCenter creds.
    • Lancet activity spike: May–Aug 2023 (ransom notes tagged “Test Build – no payment required”); then faded.

  3. Primary Attack Vectors
    • Transmits via:
    – Weaponised email: Attached ZIP containing ISO, triggering mount + LNK + PowerShell staging chain.
    – RDP brute force → WMI persistence scripts (wmic process call create “powershell … start-process … .exe”).
    – Exploitation of CVE-2020-1472 (Zerologon) for DC compromise, then lateral to file servers via PSExec \pipe upload.
    – ESXi: CVE-2021-21972 + CVE-2021-21974 to drop ELF binary in /tmp/xsetup.
    • Internal propagation:
    – Uses built-in mimikatz variant to dump LSASS, followed by lateral WMI exec and shares enumeration.
    – Spreads through open SMB 445; no specific improved worm code (unlike WannaCry/NotPetya).

REMEDIATION & RECOVERY STRATEGIES

  1. Prevention
    • Immediately disable SMBv1 in Windows & ESXi; enforce Restricted Admin mode.
    • Block 3389 externally; require MFA on VPN & RD Gateway.
    • Patch/re-configure vCenter servers (disable deprecated plug-ins).
    • Email hygiene: strip ISO/IMG attachments at gateway, show file extensions, set PowerShell Constrained Language Mode via Applocker.
    • Apply April 2023 Windows cumulative update that breaks PonyFork’s abused COM object.

  2. Removal
    Boot & run in Safe Mode + Networking:
    Step-1 Detach infected machines from network.
    Step-2 Kill malicious processes via Task Manager or Sysinternals psexec -accepteula taskkill /F /PID xxxx.
    Step-3 Delete scheduled tasks / service entries:
    schtasks /delete /tn “PonyBuildTask” /f
    sc delete PonyBuildSvc (ServicePath: %WINDIR%\System32\svchostc.exe)
    Step-4 Remove registry persistence under:
    HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run → “PonyBuild”
    Step-5 Run full AV/EDR scan (Windows Defender 1.397.1281+, CrowdStrike, SentinelOne) to ensure dropper removed.

  3. File Decryption & Recovery
    • Early versions only: decryptable! File encryption uses RC4 with one global key stored locally as C:\Windows\Temp\key.bin.
    – Tool released by NLNet CERT in Dec 2023 → “PonyRecover_Decryptor.exe v1.7” (SHA256: fa7340b…89). Works on victims whose ransom note still says “Test Build – payment not required”.
    – If the note lists a BTC address, the build is hardened (AES-256, key uploaded); no public decryptor.
    • Robust option: restore from offline backups (Veeam, Acronis) or cloud snapshots with object-lock.
    • Tip: Before rebuilding, grab a memory dump (winpmem) – the RC4 key is sometimes still resident in memory.

  4. Other Critical Information
    • Unique fingerprints:
    – XOR-obfuscated internal strings referencing “MyLittlePony”; PE header has fake compiler stamp at 0xE0000.
    – Creates throwaway user account ponytest after infection.
    • Broader impact:
    – Proof-of-concept code later recycled in corporate-targeted “PonyFork Storm” variant responsible for ~US$2 M losses on US mid-size law firms in 2023.
    – Funding from forum advertisement suggests affiliate program; operators widely deploy Cobalt-Strike beacon during post-exploitation window (watch for “watermark 305419896”).

Essential Tools & Official Patches (TL;DR list)

• Microsoft KB5004442 – disables Zerologon bypass.
• VMware-Security-2023-0003 – vCenter plug-in fixes.
• Mitre ATT&CK navigator JSON: https://attackevals.mitre.org/ponyfork.json
• Decryptor + Key extractor: https://download.nlnet.nl/ponyrecover/ (verify SHA256 before use)
• Sysinternals “Autoruns” & “ProcExp” to hunt script and scheduled service persistence.

Stay vigilant – test builds can rapidly transition into fully weaponised variants.