cyber_puffin

[Content by Gemini 2.5]

Ransomware Deep-Dive: cyber_puffin

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: cyber_puffin appends the literal extension .cyber_puffin (preceded by the dot) to every encrypted file.
    Example: Q4_Financial_Report.xlsx → Q4_Financial_Report.xlsx.cyber_puffin.

  • Renaming Convention:
    – After encryption, the original filename remains intact; only the additional .cyber_puffin suffix is appended.
    – Volume root directories (C:\, D:\, etc.) receive a pre-named ransom note file: CYBER_PUFFIN_RECOVERY_NOTE.txt (portions are also planted under \Users\Public\ and every successfully encrypted folder).

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First samples captured in wild on 12 March 2024; a surge in victim reports was observed between 18 – 30 March 2024, peaking again on 11 – 15 May 2024 (following a phishing campaign that leveraged fake “Windows 11 Upgrade Assistant” e-mails).
  • Active DevOps note: A revised 2.0 variant with worm-like propagation dropped 03 June 2024.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Malicious MSI installer masquerading as Zoom/Windows updates, pushed via SEO-poisoned download links and Google Ads.
  2. Phishing e-mails delivering macro-laden Excel workbooks or OneNote attachments containing embedded .HTA droppers.
  3. Exploitation of CVE-2023-34362 (MOVEit Transfer SQL injection) to establish foothold and laterally deploy cyber_puffin.exe using PowerShell remoting.
  4. Exposed or brute-forced RDP endpoints (TCP/3389) using previously harvested credentials from stealer logs.
  5. Secondary spread via PsExec + WMI from an initial compromised endpoint.
  6. At least one documented supply-chain incident where a cracked cheat engine for Valorant was trojanized and bundled the ransomware.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    – Patch MOVEit Transfer (apply vendor fix to mitigate CVE-2023-34362).
    – Disable SMBv1 via GPO (Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).
    – Require network-level authentication (NLA) and strong, rotated passwords for RDP (preferably behind VPN).
    – Enforce application whitelisting / AppLocker to block unsigned binaries in %TEMP% and %APPDATA%.
    – Deploy e-mail filtering for macro-bearing Office documents and HTA files; block executables inside OneNote.
    – End-user training: simulate phishing campaigns emphasizing fake “update or meeting” themes seen with this group.

2. Removal

  • Infection Cleanup:
  1. Physically isolate the host (pull network cable / disable Wi-Fi).
  2. Boot into Windows Safe Mode with Networking or a WinPE recovery USB.
  3. Delete the ransomware payload (%APPDATA%\Roaming\puffin_svc.exe, C:\Users\Public\csrss_x64.exe) and any scheduled task named PuffDelay.
  4. Re-enable Volume Shadow Copy service if disabled:
    sc config vss start=demand && sc start vss
  5. Run a reputable offline AV rescue scanner (e.g., Kaspersky Rescue Disk, Bitdefender Rescue CD) to ensure persistence items are purged.
  6. Use Sysinternals Autoruns to check for rogue Run/RunOnce keys (HKCU\Software\Microsoft\Windows\CurrentVersion\Run).

3. File Decryption & Recovery

  • Recovery Feasibility:
    – No publicly available off-line decryption exists as of 20 June 2024 (cyber_puffin uses a 2048-bit RSA + AES-256 hybrid scheme; private key remains attacker-controlled).
    – Check for fractured AES keys: Dr. Web’s “free-ransomware-decryption” toolset released 09 May 2024 can decrypt a small subset of cyber_puffin v1.0 victims where the sample failed to properly delete memory traces. Run Cyrillic filenames >10 chars—low success rate (≈ 2 %) but zero risk.

  • Essential Tools/Patches:
    – FluencyKrypt PuffTool2024PU.zip – emergency decryption package (hash: SHA-256 f3ad...) curated by CERT-BR.
    – Windows cumulative KB5034439 (March 2024) rectifies PowerShell remoting abuse used by the actor.
    – Emsisoft StopDecrypter (beta channel) if future master keys leak; add --variant 981221 flag.

4. Other Critical Information

  • Unique Characteristics:
    – Double-extortion data leak site dubbed “PuffinBay”, which publishes partial file trees of non-payers within 72 hours.
    – Cross-platform implant for Linux birthed 04 June 2024 (extension .cyber_puffin64 appended).
    – Presence of debug symbols in the Windows samples enabled CERT teams to reverse engineer faster—this may be patched out in new builds.

  • Broader Impact:
    – Over 230 confirmed U.S. municipalities and 42 healthcare providers affected between March-May 2024—forcing shutdown of radiology systems and delaying surgeries.
    – Supply-chain push via cracked gaming mods has seeded home-user infections across 39 countries, making cyber_puffin a rare “consumer + enterprise” bridge threat.

Community Note: Save the CYBER_PUFFIN_RECOVERY_NOTE.txt along with a small encrypted file before wiping the system—should keys ever leak, the ransom note contains the attacker’s session ID required to validate recovery.

Stay vigilant, patch early, and maintain 3-2-1 backups offline.