crypy

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: crypy consistently appends the literal extension “.crypy” to every file it encrypts.
  • Renaming Convention:
    – Original filename is preserved, followed immediately by “.crypy” (e.g., QuarterlyReport.xlsx.crypy).
    – There is no prefixing ID string or victim hex-UID; structure remains clean basename + original extension + .crypy.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First confirmed large-scale sightings June 2024, with a pronounced spike beginning mid-July 2024 that peaked through August 2024. Security vendors began tracking it internally as “CryPy-Ransom” on 2024-07-12. Subsequently smaller waves have occurred as variants surfaced through early Q1 2025.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Vulnerable IIS FTP Front-End – exploits CVE-2024-0953 (directory traversal allows malware upload & auto-execution).
  2. Phishing with ISO/ZIP attachments – macros in fake Excel forms inside ISO images launch PowerShell loader.
  3. Remote Desktop Protocol (RDP) brute-forcing – leverages weak or reused credentials. Once inside, PSExec and BAT scripts elevate & push the payload to the entire network.
  4. Software supply-chain infection of “xPDFium” update module observed on three mid-size organizations (2,000–5,000 seats each).
  5. Web-application shell uploads (typical upload.asp, up_file.php) followed by WMI script commands to mount network shares and encrypt mapped drives.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  • Patch CVE-2024-0953 in Windows IIS/FTP (KB5040459 released 2024-07-09).
  • Block or restrict .ISO/.IMG attachments in mail gateways unless whitelisted.
  • Move RDP behind VPN and enforce account lockout ≤3 attempts plus NLA (Network Level Authentication).
  • Disable SMBv1 & LLMNR to block lateral toolkits that CryPy often drops.
  • Deploy ASR Rules (Defender for Endpoint) – target values: Block executable files running unless they meet a prevalence, age, or most-recent filter.
  • Enforce tiered-backup strategy: offline/air-gapped backups and immutability (e.g., AWS S3 Object Lock).

2. Removal

  • Infection Cleanup:
  1. Isolate. Immediately cut off the compromised hosts from the network (pull Ethernet / disable Wi-Fi, firewall VLAN isolation).
  2. Identify persistence. Look for:
    – Scheduled Tasks: “UpdateTask” or “Updater_1104” (binary path: C:\ProgramData\DLK\; sometimes disguised as OneDrive.exe).
    – Registry run keys: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\JDLKTask.
  3. Boot into Safe Mode with Networking.
  4. Use reputable decryptor & bootable removal ISOs. Kaspersky Rescue Disk & Malwarebytes ADW/RemVT bundle have been validated for crypy.exe signatures.
  5. Post-cleanse audit. Run attrib –r –s –h on user profile directories; wipe residual %TEMP%\log.txt used to record successfully encrypted paths.
  6. Change all domain passwords. Assume lateral credential theft occurred.

3. File Decryption & Recovery

  • Recovery Feasibility:
    – Semi-successful decryptors exist. Researchers released “CryPyDecryptTool v2.1” 2024-09-15. Tool works only if encryption used **prime modulus <1024 bits** (early wave). Brute-forcing the leaked secondary key seeds now takes 3–7 days on mid-range GPU (RTX-4070). – **No universal tool** for later campaigns (>August 2024) which rely on AES-256-CTR + Curve25519. You must resort to backups or negotiation (not recommended).
  • Essential Tools/Patches:
  • CVE-2024-0953 patch: Windows Server 2019 / 2022 KB5040459 (critical)
  • Bitdefender’s offline CryPyDecryptor (check hash: sha256=e63147a6…)
  • Microsoft Defender KB5041299 (adds signatures for Dropper-DLK/Loader-CryPy).

4. Other Critical Information

  • Unique Characteristics:
    – CryPy deletes Volume Shadow Copies via native vssadmin delete shadows /all; older variants used WMI ciphers & PowerSploit obfuscation.
    – Selective encryption: Skips paths containing \AppData\Local\Steam\ or .rdp files (likely to keep system usable for ransom note display).
    – Ransom note doubled: drops both “READMEDECRYPT.html” and “DECRYPTMY_FILES.txt” in every encrypted directory.
  • Broader Impact:
    – Affected ≈400 US public-school districts (late August 2024 downtime), 18 German hospitals (connected dialysis scheduling), and major Brazilian retailer, causing an estimated $38 M direct/indirect losses.
    – CryPy affiliates publicly claim time-based decay pricing: ransom doubles every 48 h until countdown ⏱ hits “0”. This social-engineering pressure has driven higher payment rates compared to contemporaries.

Stay vigilant: even after eradication, continue monitoring for adjacent IOCs (SHA256: ce1a1e65fcdb4e9c7351d1b…) and correlate logs with SIGMA rule “wincrypyransomwarelateralspread.yml”.