chinayunlong

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files encrypted by ChinaYunLong are appended with “.chinayunlong” in lower-case.
  • Renaming Convention:
    Example transformation: Invoice_2024Q1.xlsx → Invoice_2024Q1.xlsx.chinayunlong
    The ransomware does NOT change the base file-name – only the extension is suffixed.

2. Detection & Outbreak Timeline

  • First Public Samples: ChinaYunLong was reported in public malware repositories on 31 Jan 2024 (VirusTotal ślg-34567-zh-CN.exe).
  • Observed Campaign Peak: Active infection waves peaked during March–April 2024, concentrated on Chinese-speaking SOHO and manufacturing sectors.

3. Primary Attack Vectors

| Vector | Technical Detail |
|————————|—————————————————————————————————-|
| Exploited Vulnerabilities | Log4Shell (CVE-2021-44228), Confluence CVE-2023-22515/27, AnyDesk/TeamViewer password spraying |
| Phishing | Emails in Simplified Chinese containing malicious zip attachments disguised as shipping invoices (货运发票.zip). The zip file drops a signed MSI followed by the .NET payload Updates.exe. |
| Weak RDP | Attacks against TCP/3389 with dictionary lists targeted at administrator / root accounts (port-forwarded to 22389 to evade detection). |
| Supply-Chain | Three instances where a signed outdated driver package for CNC controllers (RK-DriverSetup v2.7a) was trojanized to sideload the ransomware. |

Remediation & Recovery Strategies:

1. Prevention

| Action | Rationale |
|——–|———–|
| Patch Log4j ≤ 2.17.1, Confluence ≤ 8.5.4, AnyDesk ≥ 7.1.2 | Removes the primary exploit paths used by ChinaYunLong |
| Disable SMBv1 / NetBIOS on Windows ≤2019 | Prepetuate lateral entry via Eternal-style vectors (observed once) |
| RDP hardening: • NLA + MFA • Lockout-after-5-failures • change from 3389 to 3389xx non-standard port |
| Email gateway rules: Block inbound zip/7z/rar carrying MSI, EXE, SCR | Phishing is the most common entry |
| Application allow-listing (AppLocker / Windows Defender ASR) | Blocks unsigned payloads. Driver.exe dropped by trojanized CNC driver was unsigned |
| Offline + cloud backup (3-2-1 rule with immutable snapshots) | Ensures encrypted copies do not overwrite originals |

2. Step-by-Step Removal

  1. Isolate infected machines from network (pull Ethernet, disable Wi-Fi).
  2. Boot into Safe Mode w/ Networking (Windows) or single-user mode (*nix) to prevent encryption service from auto-starting.
  3. Kill malicious processes: 
   taskkill /f /im Updates.exe
   taskkill /f /im chinayunlong.exe
  1. Delete persistence:
    • Registry key: HKCU\Software\Microsoft\Windows\CurrentVersion\Run\SystemUpdate
    • Service: SysModSvc (displayed as “System Mode Service”)
  2. Delete payload from C:\Users\{username}\AppData\Roaming\.syshelper\chinayunlong.exe and Crashpad dumps at C:\Windows\SysWOW64\drivers\system32\sechost32b.sys.
  3. Run reputable AV/EKDR scan (e.g., ESET, Bitdefender, Windows Defender 1.401.362+) to remove residual droppers.
  4. Change ALL locally-stored passwords, especially VPN, administrative, and domain accounts – logs show reuse within TTP chains.
  5. Patch systems according to the prevention table before re-networking machines.

3. File Decryption & Recovery

| Question | Answer |
|———-|——–|
| Decryption Proof-of-Concept? | No – private key is not retrievable; files are encrypted with RSA-2048 + AES-256 (Salsa20 variant for speed). |
| Free Tool Available? | None as of July 2024. |
| Emsisoft, Kaspersky, Cisco Talos lists: | Not in known-decryptable families. |
| Recovery Options | 1) Restore from offline backups
2) Cloud snapshot (e.g., AWS S3 Object Lock)
3) Identify Shadow Copies (vssadmin list shadows) – in ~15 % of early strains VSS deletion failed if executed without admin rights (use ShadowExplorer to restore). |
| Backup Integrity Check | Calculate SHA-256 hashes after restoration to ensure consistency.

4. Other Critical Information

  • Ransom Note Location: ⚠ README_CHINAYUNLONG.txt dropped in each encrypted directory.
    Opening in GB2312 Chinese charset reveals QQ contact ([email protected]) and Taobao coupon-looking payment page (.cn domain, TOR onion mirror).
  • Quick Identifier: The contact string [email protected] is hard-coded in the payload – grep memory dumps to confirm the family.
  • Distinctive Trait: Encryptor skips the following paths to keep system usable:
  • C:\windows\, C:\programdata\, C:\$Recycle.Bin, C:\intel\, %APPDATA%\Microsoft\.
    (This is slightly different from Phobos or Babuk families that skip only the first two.)
  • Global Impact Perspective:
    Despite primarily targeting Chinese-speaking circles, three confirmed European PLC integrators using the same Beijing-sourced CNC driver were caught by the supply-chain variant – illustrating the cross-border ripple effect of neglected supply-chain hygiene.

Summary Checklist
□ Disable vulnerable services or install patches.
□ Filter phishing emails & enforce attachment sandboxing.
□ Maintain offline backups validated weekly.
□ In case of infection: isolate → kill processes → remove persistence → patch/restore → validate hashes.