cry128

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files encrypted by Cry128 (categorized under the CrySiS / Dharma family) receive the appended extension “.cry128”.
  • Renaming Convention: Example – 2024-05-15-Invoice.pdf ⇒ 2024-05-15-Invoice.pdf.id-XXXXXXXX.[[email protected]].cry128
    Variant 1: [EMAIL_EXT].cry128 (two parts after the original file name).
    Variant 2: Some samples insert a victim-UID in square brackets: filename.[victim-UID].[email].cry128.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First large-scale reports surfaced late-October 2016 when security researchers publicly tied the “Cry128” extension to a new module inside the CrySiS family. Secondary waves continued into early-2021, particularly when operators switched to cracked RDP or MSP tooling (e.g., through Kaseya VSA).

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. RDP Compromise – brute-forced, bought credentials, or unpatched BlueKeep (CVE-2019-0708) before mitigation.
  2. Phishing & Malicious Attachments – ISO, ZIP or macro-enabled Office files delivering the Cry128 dropper via spam campaigns.
  3. Exploit Kits / Drive-by Downloads – historical use of RIG EK, later Angler/Fallout EK to push “Cry128” loader.
  4. Lateral Movement via SMB – internal spread after initial foothold using PSExec and stolen NTLM hashes (though NOT the EternalBlue vulnerability).
  5. Supply-chain poisoned software updates – 2020-2021 incidents showed attackers compromising MSP Remote Support tools, then pushing Cry128 payloads en-masse.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  • Disable or restrict RDP via VPN-only access, enable Network Level Authentication (NLA), enforce 2FA, and log/log-ship all RDP events.
  • Segment networks; block lateral SMB (ports 445/135/139) between end-user VLANs unless explicitly required.
  • Patch externally facing Windows systems against BlueKeep (CVE-2019-0708), double-check expired EOS systems (Win7/2008).
  • Deploy mail-filtering capable of ISO/ZIP deep-inspection and macro blocking.
  • Use application whitelisting (Windows Defender Application Control / AppLocker) to disallow unsigned binaries.
  • Maintain 3-2-1 backups (three copies, two media, one off-line/immutable). Test restoration monthly.

2. Removal (Infection Cleanup)

  1. Isolate – cut the host from all networks (LAN/Wi-Fi/Ethernet), disable Wi-Fi adapters.
  2. Collect Volatile Artifacts – take RAM dump if forensics is required.
  3. Boot from Clean Media – BitLocker/VeraCrypt/PXE to WinPE/LiveUSB.
  4. Delete malicious services & registry keys typically located at:
  • HKLM\SYSTEM\CurrentControlSet\Services\windisk.sys (randomly named kernel driver)
  • HKCU\Software\Microsoft\Windows\CurrentVersion\Run\{RandomName} entry pointing to %APPDATA%\[random].exe
  1. Remove executables from common drop locations:
  • %WINDIR%\System32\[random].exe
  • %APPDATA%\Microsoft\Windows\[random]\[random].exe
  1. Purge Scheduled Tasks – check TASKSCHD.MSC for “SystemAuxiliary” or similar bogus names.
  2. Restart into safe-mode w/ networking, run a full scan with updated ESET, Kaspersky, Bitdefender, or Microsoft Defender signatures.
  3. Validate – re-scan with offline AV (KVRT, Sophos bootable, Malwarebytes PE). Only reconnect to LAN when 100 % clean.

3. File Decryption & Recovery

  • Recovery Feasibility: Yes – official decryptor exists (ESET CrySiS Decryptor, Kaspersky RakhniDecryptor, and Avast). Keys for Cry128 released by the original master recovery dataset (leaked private keys from December 2016) still work.
  • Steps:
  1. Confirm File Type remains intact – run cry128_decrypt.exe -scanonly to see key header.
  2. Copy an original/unencrypted file (pre-breach backup) plus its encrypted pair to the same folder.
  3. Run decryptor with elevated rights (cmd → runas). If key retrieved, mass-decrypt with -dir C:\.
  4. Verify file integrity; do incremental restore of missing files from backups.
  • Essential Tools/Patches:
  • ESETCrysisDecryptor.exe (latest v2.0.0.1) – works offline.
  • Kaspersky RakhniDecryptor 3.2 (2024) – GUI/CLI mode.
  • Microsoft KB4499175 (May-2019) – patches for BlueKeep retroactively applied to Win7/2008 R2.
  • Sysinternals Autoruns / Process Explorer – for deep TA clean-up.

4. Other Critical Information

  • Unique Characteristics:
  • Cry128 retains the original file size – no data exfiltration noted prior to encryption (version considered pure “locker”).
  • Uses RSA-1024 + AES-128 ECB for fast encryption.
  • EXT-data section stores encrypted AES key + author ID; format differs slightly from Cry36/Cry9 variants.
  • Broader Impact:
  • Healthcare sector (HCOs) suffered the heaviest losses in 2017-2018 waves due to legacy RDP exposure.
  • Cryptographic overlap with Cry36 led to flawed “payment” sites – victims paid twice before realising decryptor already existed.
  • Regulatory fines in EU (post-GDPR) reached €2 M total for inadequate incident response timing involving Cry128.