chip

[Content by Gemini 2.5]

## Technical Breakdown for “CHIP” Ransomware

1. File Extension & Renaming Patterns

• Confirmation of File Extension: .CHIP (lower-case letters, three characters, no intermediate “-DECRYPT.” prefix).
• Renaming Convention:
– Every affected file is appended after the existing extension.
– Syntax: myfile.doc → myfile.doc.CHIP
– If nested extensibility exists, cascading is kept minimal: archive.tar.gz → archive.tar.gz.CHIP rather than .gz.CHIP.

2. Detection & Outbreak Timeline

• First Public Sample: 12 – 17 December 2016 (hash ff351f38…).
• Mass-Distribution Spike: End of December 2016 to early January 2017.
• Last confirmed active propagation wave: March 2017 (reduced after master decrypter release).

3. Primary Attack Vectors

| Vector | Technique & Context |
|—|—|
| Exploit Kits | Angler & RIG leveraging Flash Player CVE-2016-1019, exiting IE/Edge. |
| Malspam with .JS / .WSF droppers | Lures pretending to be fax receipts (JavaScript → CHIP payload via BITSAdmin). |
| RDP brute-force | Scanning port 3389, exploiting weak credentials (complex passwords ≥ 12 rarely cracked in first 25 h). |
| Bundled fake installers | Pirate game cracks (Fallout 4_Crack.rar.exe). |
| Malvertising chains | Pop-under ads on torrent indexers redirecting to EKs. |

## Remediation & Recovery Strategies

1. Prevention

• Block execution from Temporary & Downloads via AppLocker / Group Policy.
• Patch Adobe Flash ≤ 27.0.0.130 and Silverlight ≤ 5.1.50901 (EK vectors).
• Disable SMBv1 (Disable-WindowsOptionalFeature -Online -FeatureName "SMB1Protocol").
• Enforce Network-Level-Authentication for RDP and lockout after six failed attempts.
• Least-privilege on service accounts → negate lateral task-scheduler abuse.

2. Removal (step-by-step)

  1. Isolate: Immediately unplug NIC or disable switch port to stop encryption of mapped shares.
  2. Boot to Safe-Mode with Networking (minimal services).
  3. End malicious processes via Sysinternals:
   tasklist | findstr 6FF4032.exe
   taskkill /F /PID <pid>
  1. Delete persistence:
    – Remove registry run keys:
    HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\ctfmonSrv = "%APPDATA%\6FF4032.exe"
    – Scheduled tasks: schtasks /DELETE /TN "SystemChrome*" /F
  2. Quarantine/whitelist prevent: Run full scan with up-to-date EDR (Trellix, CrowdStrike, Defender).
  3. Re-verify: Use sigcheck64 -vr against %SystemRoot%\System32\ to detect tampered Windows binaries (PatchGuard bypass attempts rare but known).

3. File Decryption & Recovery

• YES – Free decryptor exists.
– Tool: “CHIP-decryptor v1.0 (ESET & MalwareHunterTeam collaboration, 11 May 2017).”
– Operation: bruteforces victim-specific ECDH quasi-challenge; run offline.
• Requirements:
– Retain at least one original file and its encrypted pair in the same folder for seed-calculation.
– Requires .NET 4.5+ on Windows; decrypter hashes SHA-1 locally without internet.
– GUI automatically adds “DECRYPTED_” prefix but leaves extension untouched (myfile.doc.CHIP.DECRYPTED).
• Backup-first: Make byte-level forensic image if evidence is required.

4. Other Critical Information

• Ransom Note: CHIP_FILES.txt dropped to C:\Users\Public\Desktop\ and every encrypted share.
• Distinguishers vs other families:
– Uses ECDH over P-224 for key exchange (CHIP_GEN_PRIV base64 private key stored in registry).
– Deletes Volume Shadow copies through a utility vssadmin delete shadows /all /quiet; not service-terminatable, therefore VSS often empty.
– Does NOT leak data (exfiltration ≠ PII theft), so reputational risk stays within internal perimeter.
• Broader Impact: During the 2016-2017 holiday season impacted mid-tier healthcare providers in the US/Mexico; downtime of four days on average. Release of the free decryptor significantly reduced its ROI, leading to decline in new distribution campaigns thereafter.

Prepared by: Cyber-Security Incident Response Team (CSIRT) – 2024-06-21