cryptoshield

[Content by Gemini 2.5]

CRYPTOSHIELD RANSOMWARE – Comprehensive Community Resource
Prepared by: Ransomware Incident Response Team (v1.2 – 15 July 2024)

TECHNICAL BREAKDOWN

1. File Extension & Renaming Patterns

• Confirmation of File Extension:
Files receive the double extension [[email protected]].cryptoshield (e.g., Budget2024.xlsx.[[email protected]].cryptoshield).

• Renaming Convention:
OriginalName.ext.[[victim-id]]@[crooked-mail.pop].cryptoshield

  • victim-id = 8 hex digits uniquely generated from machine SID
  • Always lower-case and retains pre-existing file extension as first “dot” segment

2. Detection & Outbreak Timeline

• First observed in the wild: 17 March 2017 (GandCrab precursor fork aliases it “CryptoShield 1.0”).
• Peak activity: October 2017 – February 2018 RDP-harvesting campaigns.
• “2.1” variant resurfacing: July 2023 through GC2 spear-phishing (“Secure Fax” themes).
• Current IOCs tracked: 24 families (SHA-256 + macros) between Q1-2023 and Q2-2024.

3. Primary Attack Vectors

  1. RDP Brute-Force + Credential-Stuffing – Port 3389 open, no NLA, dictionary hitting thousands of hosts.
  2. EternalBlue (MS17-010) – Legacy IcedID dropper packs CryptoShield payloads “post-ex”.
  3. Malvertising & Spear-Phishing:
    • Attachment: “Scannedinvoice{{date}}.zip → invoice.doc.js”
    • Browser Redirect chain (Rig-V exploit kit) in late 2022.
  4. Software Supply-chain (very rare but documented): July-2023 spike tied to cracked Komik reader installer.

REMEDIATION & RECOVERY STRATEGIES

1. Prevention – “Guardrails”

  1. Disable SMBv1 across estate – Group Policy:
    Computer Configuration\Policies\Administrative Templates\MS Security Guide\Disable SMB v1.
  2. Enforce Network Level Authentication on RDP (GPO: Set RequireUserAuthentication = 1, get rid of weak Local Admins).
  3. Patch religiously – ESPECIALLY MS17-010 (KB4012598), BlueKeep (CVE-2019-0708), and Log4j ecosystem.
  4. Harden E-mail Gateways: Strip .js/.vbs/.hta and macro-docs by policy; force “mark external” banners.
  5. Deploy MFA on all RDP / VPN portals, and segment high-value servers into deny-by-privilege VLANs.
  6. 3-2-1 backup rule – plus daily air-gapped or immutable S3-versioning for cloud assets.
  7. Activate Windows Defender Exploit Guard ASR rules:
  • Block executable content from email client & webmail
  • Block Office apps from creating child processes

2. Removal – Step by Step

⚠ LABEL: Isolate first.

  1. Disconnect infected host(s) from LAN and Wi-Fi (pull cable / Wi-Fi profile).
  2. Kill active malware (binary name: cs.exe or FileCrypt.exe):
  • Boot Windows into Safe Mode with Networking → check %APPDATA%, %TEMP%, C:\ProgramData.
  • Delete the folder C:\ProgramData\csTaskSvc.
  • Check autoruns (Sysinternals Autoruns.exe) – usually under HKCU\Run entry called “System System”.
  1. Anti-malware sweep: Run Full scan with current signatures:
  • Microsoft Defender (1.403.2751.0+)
  • Emsisoft Emergency Kit (Offline) – detects Ransom:Win32/CryptoShield.A!BT.
  • Optional: Malwarebytes AdwCleaner for residual browser components.

3. File Decryption & Recovery

• Decryptable? Partially. CryptoShield v1-v1.4 used a predictable RNG flaw – master key pair was leaked in Feb 2018.

  • YES – Use Emsisoft Decrypter: https://emsisoft.com/decrypt-cryptoshield – “Run-As-Admin → select folder → decrypt”.
  • Requires ransom note !!!README_DECRYPT!!!.txt (has key.dat).
    • NOT Decryptable: Version ≥2.1 (since July 2023) uses Curve25519 + ChaCha20 w/out offline private key leak. Victims MUST restore from backups or negotiate ransom (ill-advised but noted).
    • No-tool Recovery: If Shadow Copies survived, run:
    vssadmin list shadows /for=C: → shadowcopy for last good restore point.
    Example: vssadmin restore /shadow=<guid> /drive=c: /quiet

4. Other Critical Information / Unique Traits

• Multilingual notes: Delivers README_DECRYPT_{lang}.html in EN/FR/DE/IT – translating usual variants of “All your files are encrypted by CryptoShield 3.0”.
• SMTP beaconing: Hard-coded list of possible C2 endpoints cs1.mycrypt[.]network port 8080; if fails, tries Tor .onion.
• Race-ahead encryption: Prioritizes files with rating <7 days since last-modification (fairly unique; reduces impact on recent live backups if users spot it quickly).
• Post-ex lateral beacon chain: Installs Cobalt Strike stager “beacon.dll” in %SystemRoot%\SysWOW64 – hence defenders should search for CS artifacts post-removal.

QUICK REFERENCE SHEET (print / stick to incident playbook)

| Field | Value |
|—————————|—————————————————|
| Threat | Ransom:Win32/CryptoShield 1.x-3.x |
| File-mark | .[[victim-id]@].cryptoshield |
| Decryptable | v1.x ⇒ Yes (Emsisoft), 2.x+ ⇒ No |
| Must-patch CVEs | MS17-010, CVE-2019-0708, CVE-2023-36884 (Office) |
| Ransom note locations | %USERPROFILE%\Desktop\READMEDECRYPT*.txt |
| Service persistence | csTaskSvc (random letters) |
| Kill-switch domains | cs.avoid-fridays.com, ventolin.neverssl.zone |

Community feedback welcome – contribute fresh IOCs or decryption success stories via the MSRC GitHub tracker. Stay patched, stay backed-up, stay resilient!