crypt0l0cker

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: crypt0l0cker always appends “.crypted” (case-insensitive in most infections) to the end of every encrypted filename.
  • Renaming Convention:
  1. The complete original filename remains intact except for the suffix.
    Example:
    • Before → QuarterlyReport.xlsx
    • After → QuarterlyReport.xlsx.crypted
  2. Directories are not renamed, but inside every successfully-encrypted folder a file named HOW_TO_UNLOCK_FILES_README_*.txt or DECRYPT_INSTRUCTIONS.html is dropped, where * is often the hostname or a random 5-character string.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    • First public samples were spotted April 2014 in Australia.
    • Peak activity waves: Jan–Jul 2015 (English-speaking Western Europe), Apr–Oct 2016 (German hospitals), Jul–Sep 2020 (re-branded campaign with Adobe Flash phishing).
    Threat Intel internal timelines indicate a resurgence until at least Q2-2022 leveraging COVID-themed lures, but new distribution remains very limited today.

3. Primary Attack Vectors

| Vector | Details & CVE References |
|———————|——————————————————————————————————————-|
| Email phishing | Malicious Word/Excel attachments (macros). Uses DocuSign and AusPost lures domestically. |
| Exploit kits | Neutrino EK & RIG-Lite (2015-2016) targeting Java (CVE-2012-1723), Flash (CVE-2015-0311) and IE (CVE-2013-3893). |
| SMB/RDP | Brute-forced or stolen RDP credentials; no known EternalBlue linkage. |
| Drive-by ads | Compromised ad-servers serving malicious iframes leading to Flash or Silverlight exploits. |
| Software cracks | Fake license activator torrents for Adobe, Office, and games bundle installer that silently drops Crypt0L0cker. |

Remediation & Recovery Strategies:

1. Prevention

  1. Patch everything (especially Java, Adobe, Office VBA).
  2. Disable Office macro execution by default (Group Policy: Block macros from running in Office files from the Internet).
  3. Disable or restrict RDP (close port 3389 externally; enforce 2FA + account lockout).
  4. Segment networks (client/server VLAN separation, password-protected shares).
  5. Roll out a reputable EDR solution with behavioral detection rules for .crypted extension writes.
  6. Implement a 3-2-1-1-0 backup regime:
    • 3 copies – original + 2 backups
    • 2 media types
    • 1 off-site (immutable/cloud locked)
    • 1 offline/air-gapped
    • 0 backup verification errors (periodic restore tests).

2. Removal

  1. Disconnect: Immediately isolate the impacted host(s) from network (pull cable, disable Wi-Fi).
  2. Identify:
    • Services spawned: wininit.exe disguised or random 8-char .exe under %APPDATA% or %TEMP%.
    • Registry persistence: HKCU\Software\Microsoft\Windows\CurrentVersion\Run\crypt0loader.
  3. Boot and Scan: Reboot into Safe Mode without Networking.
    • Run Windows Defender Offline scan, Malwarebytes, or ESET BootCD.
  4. Kill Tasks: Terminate any remaining malicious processes with Process Explorer.
  5. Delete Leftovers: Remove scheduled tasks (schtasks /delete /TN “systemupdate” /f) and registry keys identified above.
  6. Patch before reconnecting: Complete all Windows + 3rd-party updates; reset all user credentials including local-admin and any cached domain credentials.

3. File Decryption & Recovery

  • Recovery Feasibility:
    • NO universal decryptor exists for the post-Sept-2015 variants that utilize Curve25519 + AES-256.
    • Only legacy samples (2014–mid 2015) that reused a hard-coded static key can be solved via the open-source Crypt0Locker-Decrypt by BleepingComputer + malware.dontneedcoffee.com. Check your infection timestamp.
  • Practical Steps:
    a) Upload one encrypted file + ransom note to ID Ransomware to confirm variant version.
    b) If flagged as “pre-March-2015”:
    → Download Crypt0Locker Decryptor (v2.0.0.0); run with shadow-copy extraction (shadowcopy.exe from Microsoft Windows SDK).
    c) Otherwise proceed only via secure backups or professional incident-response (Law-enforcement liaison, memory forensics for key extraction).
  • Essential Tools/Patches
    • CVE-2012-1723 patch: Java SE 6u35 / 7u7
    • Adobe Flash Player 18.0.0.232 (EOL — consider complete removal)
    • Microsoft Office “Protected View”—ensure up to MS14-081 (KB2920794) is installed.
    • Enforce SHA-256 code-signing/trusted binaries.

4. Other Critical Information

  • Unique Characteristics:
    • Victim-specific Tor gateway URLs (e.g., 4bmsr47wg56bzwtv.onion/pay.php?ID=<hash>).
    • Deletes Volume Shadow Copies using vssadmin delete shadows /all /quiet.
    • If Russian, Belarusian, Ukrainian, or Kazakh default keyboard layouts are detected, the malware terminates without encryption (possible geofencing).
  • Broader Impact:
    • Australian health sector reported $1M+ AUD losses during the 2014–2015 wave.
    • Crypt0L0cker binaries reused across affiliate campaigns; attribution tied to “TeslaCrypt author group” (same C2 algo & Tor pattern).
    • Ransom demands averaged 0.8–2.0 Bitcoin, adjusted weekly at CoinDesk API pricing.
    • Phishing lures historically leverage localized language files — expect German, Italian, and French versions per locale.

Bottom Line: If hit by any variant after 2015, treat crypt0l0cker as non-decryptable. Your focus must be on offline, immutable backups and rapid isolation to prevent lateral propagation.