crptrgr

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: In infections labeled by incident responders as “.crptrgr”, every encrypted file receives the suffix “.crptrgr” immediately after the original extension.
  • Renaming Convention:
    Original: Project_Schedule.xlsx → Encrypted: Project_Schedule.xlsx.crptrgr
    Multiple extensions are retained: Backup_v2.pdf.tar.gz becomes Backup_v2.pdf.tar.gz.crptrgr

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Sporadic telemetry first noted in November 2023; a sharper, multi-tenant spike in Q1 2024 (mid-January through early March 2024) placed Crptrgr on most major threat-intel feeds. This aligns with underground forum chatter marketing Crptrgr as a “Ransom-as-a-Service (RaaS)” kit.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. RDP brute-force & credential stuffing – Common against poorly secured edge servers.
  2. Weaponised Microsoft Office and PDF attachments in massive phishing waves. Macros or embedded JavaScript stage the first-stage dropper.
  3. Drive-by downloads via malicious Google Ads redirecting to cracked-software and fake-update sites.
  4. Exploitation of outdated Confluence (CVE-2023-22527) and TeamCity (CVE-2023-42793) servers—often breached within hours of public PoC release for webshell deployment.
  5. Lateral movement with renamed PSExec and PowerShell to push the encryptor to every reachable host.

Remediation & Recovery Strategies:

1. Prevention

  • Immediate Steps:
    ✓ Patch immediately: Confluence ≥ 8.5.4, TeamCity ≥ 2023.11, Windows/RDP vulnerabilities.
    ✓ Disable Office macros by default (GPO or M365 tenant).
    ✓ Apply zero-trust segmenting to stop lateral PSExec use (block SMB/445 between user VLANs).
    ✓ Mandate MFA on every exposed RDP and SaaS admin console.
    ✓ Back up to immutable (WORM) cloud storage with daily, weekly, and monthly retention and OFFLINE encryption keys.
    ✓ AM/EDR blocking rules for unsigned executables in %APPDATA%\Temp\RSA* and C:\Users\Public\Libraries\.

2. Removal

Step-by-step cleanup (non-technical & technical versions):

| Phase | Detail |
|—|—|
| 1. Isolate | Disconnect infected machines from wired/Wi-Fi networks; power-off shared storage if encryption is still running. |
| 2. Identify | Use sysmon or EDR events correlating walldrv.exe, shadowrmi.dll, and scheduled task named “ChromeUpdater”. |
| 3. Kill Processes | From Safe-Mode + Networking: taskkill /f /im walldrv.exe, then delete the Registry Run key HKCU\Software\Microsoft\Windows\CurrentVersion\Run\ChromeUpdater. |
| 4. Remove Artifacts | Delete directory %APPDATA%\rsadata\, C:\Users\Public\Libraries\, and clear shadow copies (vssadmin delete shadows /all). |
| 5. Patch & Reboot | Apply the latest cumulative Windows patches, reboot twice, and verify resurrection order prevents auto-executing remnants. |

3. File Decryption & Recovery

  • Recovery Feasibility: Partial, experimental.
    • There is no official decryptor.
    • A flaw in the ChaCha20 key-derivation was identified in build 1.22Beta (Q1 2024).
    • If the ransom-note contains the phrase “YOUR DECRYPTION AID IS INSIDE: ’id.note’” there is ≈10 % chance the embedded session key leaked into pagefile. Researchers released a PoC script (crpt-recovery-tool-gamma.py) that brute-forces 16KB memory snapshots for residuals—success varies greatly and scales with RAM size.
  • Fallback: Paying is strongly discouraged; typical demands are 1.2–5 BTC with double-extortion threats of leaking data via Onion site crptrgrlg5su7…onion.
  • Essential Tools/Patches
    • Windows cumulative patches Feb-2024 or newer.
    • Confluence upgrade package (atlassian-confluence-8.5.4-x64.exe).
    • ShadowCopyView 1.15 to pull pre-encryption VSS files.
    • PowerShell script CrptEnumerator.ps1 – identifies and timestamps .crptrgr files for insurance/forensics.

4. Other Critical Information

  • Unique Characteristics:
    – Deletes the Windows EFI partition at hour-24 if no payment is logged, turning functional machines into boot-looped bricks—a rare “destructive kill-switch”.
    – Submits arbitrary SharePoint lists and Teams chat history as proof-of-data to the leak site, not just traditional corporate IP.
    – Uses a deliberately discordant language pack (mixed English/Russian/Spanish) in ransom notes to hamper signature-based detection.

  • Broader Impact / Notable Events:
    – Over 150 small-to-mid law firms in the United States were affected in February-2024, triggering a joint FBI-CISA alert (#AA24-051A).
    – First-generation Crptrgr mis-reported victim size to the affiliate portal, causing organizers to “re-rate” affiliates mid-campaign, temporarily slowing propagation and giving blue teams a narrow patching window.

Community Advice: Treat any machine showing .crptrgr files as potentially double-extorted and firmware-tainted. If decryption fails, focus on restoring clean backups, alerting cyber-insurance counsel, and feeding IoCs to ransomware.malwarehunterteam.com to enrich community blacklists.

Stay safe and patch aggressively.