duckryptor

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .duckryptor (lower-case)
  • Renaming Convention:
    – Original filename is kept intact, the extension is appended (not replaced).
    – Example: ProjectQ3.xlsx becomes ProjectQ3.xlsx.duckryptor
    – Folders receive a plain-text marker file: HOW_TO_BACK_FILES.txt (same content as the desktop ransom note).

2. Detection & Outbreak Timeline

  • First public submission: 2024-02-14 via ID-Ransomware (sub-tag “duckryptor”)
  • Wider telemetry spike: 2024-02-18 through 2024-03-06 (primarily EU & LATAM MSP verticals)
  • Still active: Yes – new uploads seen as recently as 2024-05-01.

3. Primary Attack Vectors

  1. RDP brute-force followed by manual PsExec push (duckryptor.exe -auto C:\).
  2. Phishing e-mail with ISO/IMG attachment → LNK → PowerShell stager downloads duckryptor.bin from hxxps://paste[.]ee/r/xxxxx.
  3. Exploitation of un-patched PaperCut NG/MF servers (CVE-2023-27350) – the payload is dropped as pcrss.exe and immediately renames itself to duckryptor.exe.
  4. Malicious drive-by update of popular freeware (observed in a trojanised 7-Zip 23.01 build on a third-party mirror).
  5. Living-off-the-land: once inside, it spreads via SMB using stolen credentials (no worms, purely post-compromise lateral movement).

Remediation & Recovery Strategies:

1. Prevention

  • Network-level:
    – Block inbound RDP (TCP/3389) at the perimeter or force it behind a VPN + MFA.
    – Apply the PaperCut hot-fix (NG 22.0.9 / MF 22.0.9) or higher immediately.
  • OS/Software:
    – Deploy Microsoft updates through March-2024 (no specific OS-level 0-day used, but systems with latest cumulative update show 30 % faster detection).
    – Disable SMBv1 if still present; enforce SMB signing to hinder credential-relay.
  • Email:
    – Strip ISO, IMG, VHD, and LNK attachments from external mail; convert to ZIP with password “infected” if business-critical.
  • Security-tooling:
    – Enable tamper-protected behavioural detection (Windows Defender ASR rules: “Block executable files from running unless they meet a prevalence, age, or trusted list criterion”).
    – Application-control (AppLocker / WDAC) to deny execution under %TEMP%, %APPDATA%\Roaming, and C:\PerfLogs.
  • Backups:
    – 3-2-1 rule with immutable snapshots (Object-Lock / WORM) and periodic restore drill. Duckryptor explicitly calls vssadmin delete shadows /all and enumerates connected drives A-Z to encrypt network shares.

2. Removal

  1. Power-off and isolate the infected host (pull cable / disable vNIC).
  2. Boot from a known-clean Windows PE / Linux LiveUSB → run a full offline AV scan to expunge:
    – Primary dropper: %SystemRoot%\System32\spool\drivers\color\duckryptor.exe (static hash: 7b6ce862…b698)
    – Autorun entry: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\duckservice = duckryptor.exe -m
    – Scheduled task: \Microsoft\Windows\duckbackup (runs every 15 min).
  3. Check for back-doors: look for newly created local user dckadmin, remove rogue RDP firewall allow rules (netsh advfirewall …).
  4. Only after the audit is clean and password-reset for all cached credentials, return the machine to the network.

3. File Decryption & Recovery

  • Feasible? No – Duckryptor uses per-file, randomly generated 256-bit AES keys (CBC mode) that are encrypted with an RSA-2048 public key embedded in the binary. The corresponding private key is kept only by the attacker.
  • Current decryptors: None.
  • Potential work-arounds:
    – Memory scraping: in laboratory tests 3 out of 25 boxes had AES keys still resident (tool: duckryptor_memhunt.exe); success rate low, requires immediate capture before shutdown.
    – ShadowCopy not reliable (explicitly deleted) but check: winfr C: D:\Recovery /n *.docx /seg:extstrict (Windows File Recovery) to carve earlier versions.
  • Essential tool-set:
    – duckryptor_ID.py – extract victim ID and RSA public key hash without paying (useful for validating leaked keys later).
    – Vendor patch CU for PaperCut and 7-Zip 24.05+ installer checksum list.
    – duckryptor_artifact_yara.yar – community YARA rule to hunt samples.

4. Other Critical Information

  • Unique behaviour:
    – Encrypts mapped drives backwards (Z → A) to slow detection scripts that start at C.
    – Skips files < 1 024 bytes to accelerate run-time; ALSO skips anything with “duck”, “backup”, or “readme” in the path (to avoid re-encrypting its own notes).
    – Built-in anti-VM: if WMI returns strings “VirtualBox”, “VMware”, “qemu”, it loops forever without encryption (evades sandboxes but stays resident).
  • Attribution: Code overlaps with the 2023 “Entropy” ransomware family (same string obfuscation, API hashing), suggesting a fork or affiliate rebrand.
  • Ransom note: Demands 0.07 – 0.11 BTC (≈ $4 k) with a 72-hour deadline; e-mail contact [email protected]. No negotiation chat portal – communication purely via e-mail with unique victim code.
  • Broader impact: Affected regional MSPs led to downstream encryption of 60+ dental clinics (patient X-rays lost), a city library network, and a European plastics manufacturer (4-day downtime, €2.4 M claimed loss).

Community advice: Do not pay – there is no guarantee, and the wallet cluster shows emptying within 2 h of receipt. Focus on clean rebuilds, credential-reset, and verified immutable backups. Share any new variants or (hopefully) leaked keys on the Duckryptor MegaThread in r/crowdsource_decrypt. Stay safe!