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Cl0p (Clop) Recovery

Direct answer

Cl0p is one of the most sophisticated ransomware families, active since 2019. It specialized in exploiting zero-days in secure file transfer products: Accellion FTA (2020), SolarWinds Serv-U (2021), GoAnywhere MFT (CVE-2023-0669) and MOVEit Transfer (CVE-2023-34362) which affected 2,700+ companies globally. Focus on mass exfiltration rather than encryption. HD Doctor runs exfiltration forensics and regulator-notification support.

Cl0p often exfiltrates data without encrypting (pure extortion). Even without encrypted files, there is a 72h regulator notification obligation. Engage response immediately.

What is Cl0p

Cl0p is a RaaS operation linked to TA505 (FIN11), active since February 2019. It evolved from pure encryption to exfiltration-based extortion, exploiting zero-days in enterprise file transfer products. MOVEit campaign (May-June 2023) hit companies like Shell, BBC, PwC, Maximus, and multiple US government agencies. Uses AES + RSA for encryption when applied (extension .clop or .Cllp).

Symptoms of Cl0p compromise

  • Anonymous communication received by email/Tor listing exfiltrated files
  • 'Cl0p Leaks' darknet site mentioning the company
  • MOVEit Transfer / GoAnywhere logs with web shell installed (LEMURLOOT)
  • Abnormal outbound traffic to known Cl0p IPs
  • Files with extension .clop, .Cllp or .Cl0p (when encryption applied)
  • Note 'ClopReadMe.txt' or 'README_README.txt'

Typical Cl0p attack vectors

Cause%Recoverable?
MOVEit Transfer (CVE-2023-34362)60%Patch + exfiltration forensics
Fortra GoAnywhere MFT (CVE-2023-0669)12%Patch + forensics
PaperCut MF/NG (CVE-2023-27350)8%Patch + forensics
Accellion FTA (legacy, 2020-2021)8%Replacement + forensics
Targeted phishing7%Training + restore
Other / unidentified5%Case-by-case analysis

Distribution based on CISA AA23-158A (MOVEit) and Mandiant reports.

What NOT to do upon Cl0p identification

  1. 1.
    Do not ignore exfiltration notice without encrypted files. Cl0p often does NOT encrypt; it extorts via leak. Regulator notification remains mandatory.
  2. 2.
    Do not immediately delete MOVEit / GoAnywhere logs. Logs hold evidence of web shell upload and cURL/Python exfiltration. Preserve before any action.
  3. 3.
    Do not pay without proof of non-leak. Even paying, leaks may occur (Maximus, Shell cases). Payment does not stop third-party extortion.
  4. 4.
    Do not restore MOVEit without patch. Restoring to a vulnerable version (CVE-2023-34362) reopens the door. Apply patch CRITICALLY before bringing service back.
  5. 5.
    Do not treat as isolated case. Cl0p campaigns hit many companies simultaneously via the same vulnerability. Check CISA IoCs for your MOVEit version.

HD Doctor process for Cl0p response

Response focused on exfiltration forensics and regulatory compliance.

  1. 1

    Triage (0 to 6h)

    Identify vulnerable products (MOVEit, GoAnywhere, PaperCut), isolation, affected server snapshots, preservation of IIS and product logs.

  2. 2

    Web shell forensics (6 to 48h)

    Identify LEMURLOOT web shell (human2.aspx or similar), analyze uploads and downloads, identify credentials and exfiltrated files via IIS timeline.

  3. 3

    Exfiltration analysis (24 to 72h)

    Cross-reference IIS, firewall and MOVEit logs to identify which files were downloaded by the attacker, with hashes.

  4. 4

    Regulatory notification (within 72h)

    Support to build the notification dossier: affected subjects, data type, mitigation applied, communication plan.

  5. 5

    Hardening and report (5 to 25 days)

    Patch MOVEit/GoAnywhere, WAF in front of transfer products, continuous monitoring, EDR. Technical forensic report.

Typical SLA for Cl0p response

ScenarioTurnaround
Initial triage0 to 6h
Web shell forensics24 to 48h
Full exfiltration analysis48 to 72h
Regulator notification dossierWithin 72h after awareness
Final technical report15 to 30 business days
  • Regulator notification within 72h is a legal obligation under data protection law.

Products hit by Cl0p campaigns

FamilySupportNotes
Progress MOVEit Transfer✅ Full forensics + patchCVE-2023-34362, 2,700+ global victims
Fortra GoAnywhere MFT✅ Full forensics + patchCVE-2023-0669
PaperCut MF/NG✅ Forensics + patchCVE-2023-27350
Accellion FTA (deprecated)✅ Legacy analysisMigration recommended
Windows IIS / web servers✅ Web shell forensicsLEMURLOOT detection

Why HD Doctor for Cl0p response

  • 🔍Specialists in exfiltration forensics and web shell detection in secure file transfer products.
  • 24×7 response prioritized for tight regulator-notification cases.
  • 📋Legal-technical support for regulator notification within 72h, structured dossier.
  • 🛡️Specific MOVEit/GoAnywhere/PaperCut hardening post-incident, with WAF and monitoring.
  • 💼Real documented MOVEit campaign cases in Brazil.

FAQ about Cl0p

Does Cl0p only steal or also encrypt?

Depends on the campaign. In 2019-2022 it encrypted aggressively. Since 2023 (MOVEit, GoAnywhere) many campaigns only exfiltrate and extort via leak, without encrypting. Both modes require regulator notification if personal data is involved.

Was I affected by the MOVEit Cl0p campaign?

Check: (1) MOVEit Transfer version installed in May-June 2023; (2) presence of human2.aspx or similar web shell; (3) abnormal activity in IIS logs in the period; (4) company name in Cl0p Leaks lists. Our playbook covers all these checks.

Does paying Cl0p prevent a leak?

History shows NO. Documented cases (Maximus, Shell, PwC and others) leaked data even after payment. Payment funds more attacks and may breach OFAC. Focus on mitigation, regulator notification and subject communication.

Is there a Cl0p decryptor?

For old variants (2019-2021) Bitdefender has a partial decryptor. For recent variants (2022+) there is no public decryptor. Since many Cl0p campaigns exfiltrate without encrypting, response focus is forensics and regulator notification, not decryptor.

How long to finalize a Cl0p case?

Forensics and notification: 7 to 30 days. Restore (if encryption occurred): 7 to 30 additional days. Subject communication: 30 to 60 days. Final technical report for judicial use: 30 to 60 days.

Compromised by Cl0p?

72h regulator deadline. Engage response immediately.

Other variants