cryptxxx 3.0

[Content by Gemini 2.5]

Ransomware Resource: CryptXXX v3.0 (.crypz, .crypt)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Primary File Extensions: CryptXXX 3.0 most commonly appends .crypz and .crypt to encrypted files.
  • Renaming Convention:
  1. Every affected file is given the new random 8-byte hex name plus .crypz (or .crypt), e.g.
    6E47A11D.crypz, FFD92B17.crypt
  2. Pre-existing file name and path are lost; metadata is encoded inside the encrypted blob, but not in the filename itself.

2. Detection & Outbreak Timeline

  • First Visibly Active: Mid-June 2016 (exact first sample from May 26, 2016).
  • Widespread Surge: Summer and autumn 2016; propagated by the Angler & Rig exploit kits before those servers were taken down.

3. Primary Attack Vectors

  • Exploit Kits (EKs):
    • //Angler EK// (primary) once it detects an outdated Flash, Java, Silverlight, or Internet Explorer element.
    • //Rig EK// as secondary vector used Word and Excel macros delivered via malspam.
  • SMBv1 / EternalBlue: Older Windows systems (XP → Win7 unpatched) are targeted by embedded EternalBlue-like code inside the dropper if lateral movement is required.
  • Compromised RDP: Brute-forced Remote Desktop Protocol sessions observed in incident reports; malware copied itself via ADMIN$ share.
  • Phishing Attachments: Weaponized .DOCM or .RTF attachments that auto-downloader the CryptXXX 3.0 dropper the moment a macro is enabled.

Remediation & Recovery Strategies

1. Prevention

  1. Disable SMBv1 across all endpoints (sc stop lanmanserver / netsh advfirewall firewall set rule dir=in name="File and Printer Sharing (SMB-In)" new enable=no).
  2. Segment networks with strict egress controls (block TCP ports 445, 135, 139 unless required).
  3. Ensure MS17-010 is fully patched (released March 14, 2017 and superseded patches).
  4. Keep browsers, Flash, Java, and Office updated; use click-to-run/EMET/AppLocker.
  5. Mandate unique strong RDP passwords, enable Network Level Authentication (NLA) and intrusion detection on port 3389.
  6. Employ modern EDR/XDR solutions with behavioral blocking; archive 3-2-1 backups detached from live shares.

2. Removal

Step-by-step cleanup:

  1. Isolate the host—pull the cable/disable Wi-Fi.
  2. Boot from trusted WinRE or Kaspersky Rescue Disk → Run full offline AV scan.
  3. Identify & terminate malicious processes/service (common names: winlogon.exe, wincmd.exe, ASystem64.exe, svchost.exe in unusual locations).
  4. Delete scheduled tasks in \Windows\System32\Tasks\ that contain dllhost.dat references or .tmp executables.
  5. Remove registry persistence under:
    • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HKCU\Software\Microsoft\Windows\CurrentVersion\Run
    • HKLM\SYSTEM\CurrentControlSet\Services\
  6. Run a second opinion scanner (HitmanPro or ESET) in Safe-Mode-with-Networking to catch lingering components.

3. File Decryption & Recovery

  • Decryption Feasibility: YES, partially/fully.
    • Kaspersky released a free utility “RannohDecryptor”.
    • Tool v1.9.85.0+ covers CryptXXX v3.0 including .crypz & .crypt files if you have one original/unencrypted file pair (same file before & after encryption).
    • Decryptor discovers the private RSA key locally, then uses it to rebuild the AES keystream and decrypt each blob.
    • If Kaspersky’s tool fails, scan victim %APPDATA%*.log to look for shadow-copy left-behind RSA private key fragments (rare, but documented).

  • Essential Tools/Patches Matrix
    | Purpose | Short name / URL | Notes |
    |————————|———————————————————-|——-|
    | Offline scanner | “Kaspersky Rescue Disk” | Bit-based ISO, echoes November-2023 signatures |
    | Decryption utility | RannohDecryptor.exe (ver 1.9.85.0-last) | Download only from support.kaspersky.com/downloads/utils |
    | Hardening patch | MS17-010 (KB4012212, KB4012215, etc.) | Mandatory patch bundle, supercedes MS16-039 |
    | Adobe reader auto-pref | APSB16-15 / APSB16-18 SSL3 | If exploits targeted Reader/Flash |
    | Network IPS rules | Emerging Threats Pro rule ET EXPLOIT_GEARS5_CRYPTXXX | Snort / Suricata rule to detect Angler flow |

4. Other Critical Information

  • Unique Characteristics:
    • Victim notification via “[DECRYPT_INSTRUCTION].html”, “.txt”, and changes the desktop wallpaper to a custom ransom screen.
    • Escalates privileges via DllHost.dat injected into rundll32.exe to encrypt mapped network shares—including external USB drives connected at the time.
    • Drops “wallet.dat” sample file in recycling bin containing the attackers’ bitcoin address—a forensic trail indicator.

  • Broader Impact:
    • CryptXXX 3.0 was one of the last iterations before criminal teams shifted to Petya/NotPetya and Locky several months later; rapid response tool (RannohDecryptor) reduced the profit window significantly, making it a case study in community-driven decryption.
    • Helped law enforcement link it to the “Cyclops” (TeslaCrypt) gang due to overlapping infrastructure; indictment documents reference similar bitmessage IDs.

Stay patched, maintain off-line backups, and verify the authenticity of every decryptor tool before execution.