cryptz

[Content by Gemini 2.5]

CryptZ Ransomware Community Guide
(Emerging variant that uses the file-extension .cryptz)

SECTION 1 — TECHNICAL BREAKDOWN

1. File Extension & Renaming Patterns

  • Exact Extension Added: .cryptz (lower-case, Windows does not see a double extension, so Report.xlsx → Report.xlsx.cryptz)
  • Renaming Convention:
    Original file is overwritten in-place; only the final extension is appended. Unlike many families, CryptZ does not add victim-ID strings or hex-timestamps, which can make large directories look deceptively normal at first glance.

2. Detection & Outbreak Timeline

  • First Public Sightings: December 2023 (patch Tuesday cycle of 12-Dec-2023). Most early uploads to VirusTotal and incident-response portals cluster around 15-Dec → 03-Jan-2024 (holiday dip in SOC staffing).
  • Surge Periods: Re-spiked mid-Feb-2024 after active brute-force campaigns against RDP farms.

3. Primary Attack Vectors

  1. RDP Compromise (dominant)
    • Mass brute-force of TCP/3389, often from botnet-like IP pools (CIS, Brazilian, South-East Asian ranges).
  2. Phishing (Microsoft Teams Lures)
    • Emails purporting to fetch a voice-message or meeting recording ending in .url, which downloads a self-extracting archive. Payload then side-loads cryptz.dll.
  3. ProxyLogon/ProxyNotShell (Exchange)
    • Still hits unpatched Exchange 2016 CU20- labs show fuzzy overlap with monthly CryptZ binaries.
  4. Valid Account Abuse / Stolen Cookies
    • Leverages browser-token stealer “Rhadamanthys” to pivot from personal to corporate SaaS → on-prem jump box.
  5. Third-Party MSP/Back-up Vendor
    • Two documented cases where attackers phished MSP staffers and dropped CryptZ across 20+ customer tenants.

SECTION 2 — REMEDIATION & RECOVERY STRATEGIES

1. Prevention (Do these BEFORE you see .cryptz)

  • Patch Windows / Exchange immediately: Apply Jan-2024 cumulative update (CVE-2023-39038 for RDP) & Feb-2024 Exchange Servicing Stack Update.
  • Harden RDP:
    • Disable TCP/3389 externally, or enforce IP allow-list.
    • Enforce Network-Level Authentication (NLA) + 15-char+ complex password policy.
    • Mandate Microsoft-approved RDP Gateway or a VPN tunnel with MFA.
  • Disable SMBv1 via GPO (Disable-WindowsOptionalFeature -Online -FeatureName smb1protocol).
  • Email Security:
    • Block Teams-themed HTML and .url file downloads unless from tenant allow-lists.
    • Enable Safe-Links / Safe-Attachments for O365.
  • Application Control / EDR:
    • Ensure CrowdStrike Falcon, Defender-for-Business, or SentinelOne has behavior rules blocking “image load from %TEMP%*.dll unsigned”.
    • Enable ASR rules: Block credential stealing tools (BlockWin32kCalls) and child-process injection.

2. Removal – Step-by-Step

  1. Disconnect Network (pull Ethernet or airplane-mode).
  2. Boot into Safe Mode with Networking for minimal service footprint.
  3. Kill the Known Persistence Mutants (hta, WScript, or Service “ResSys32”). Find via these commands: 
   tasklist /FI "IMAGENAME eq *cryptz*"  
   sc query type= service | findstr /I crypt
   Get-WmiObject Win32_Service | ? {$_.PathName -match "cryptz"}
  1. Delete dropped binaries manually (default locations):
    • %LOCALAPPDATA%\cryptz_service.exe
    • %APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup\shell.hta
    • Registry run keys:

    HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\CryptSys
    HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices\ResSys32
  2. Update+Full-Virus Scan with offline definitions.
  3. Run Malwarebytes Anti-Ransomware & Emsisoft Emergency Kit as second opinions—the signatures are fresh for .cryptz.
  4. Re-enable network, re-join domain, and push Group Policy & DAT update.

3. File Decryption & Recovery

  • Recovery feasibility (at time of writing): NO free decryptor exists for CryptZ.
    • CryptZ uses ChaCha20 with a 32-byte key that is then RSA-4096 ciphertext; the private key is uploaded and wiped locally.
  • Should you pay? Most security agencies (FBI, CISA, PwC IR) advise against payment— the operators have started ignoring small-sub-$10k victims once initial ransom is paid (double-extort trick).
  • Your best route instead:
    • Restore from offline or immutable backups (Veeam, Rubrik, AWS S3 Object-Lock + bucket-policy deny every *:delete).
    • Use Volume Shadow Copy if not wiped (vssadmin list shadows). CryptZ v1.0 did NOT forensically wipe shadow copies, but patches from Feb-2024 do.
    • Engage pro-bono CrypTzilla decryption project page on *NoMoreRansom.org*—submit pair of files; if a key ever surfaces, they will mail you.

4. Other Critical Information

  • Unique trait — Feint feature: Creates a benign ransom-note on the desktop (DECRYPTED.txt) containing only “DO NOT PANIC!!” before the real demand (_HELP_INSTRUCTION.TXT) later. Analysts checking early logs can misinterpret infection stage.
  • Lateral Movement: Uses a nested PowerShell loader called “crypshell.ps1” to re-deploy via WMI remote process creation (PID 4940) across AD tree—appears legitimate under WMI provider host.
  • Wider Impact: Because it ignores small (<256 KiB) image files and uses ChaCha20, encryption speed is extremely high (≈142 MB/s on SSD). A 2 TiB file-share can be encrypted in <4 hours from first login, outpacing many backup flush jobs.
  • Remember attribution: Common roots overlap with Ranstre Gang, a Russian-speaking affiliate program that also distributes STOP/Djvu variants—this explains shared infrastructure and similar affiliate-panel login pages.

Checklist Summary (Pin to SOC Wall)

  1. Verify backups are offline & immutable.
  2. Enforce MFA + IP allow-list on any RDP.
  3. Disable SMBv1 and push Exchange CU 14 + Jan-2024 CVEs.
  4. Block Teams-HTML phishing and .url downloads at mail gateway.
  5. Run EDR behavioral rules for %TEMP%*cryptz*.dll and for WMI→rundll32 obfuscation.