decrypt2017

[Content by Gemini 2.5]

Technical Breakdown:

File Extension & Renaming Patterns

  • Confirmation of File Extension: .decrypt2017
  • Renaming Convention: The malware appends the literal string “.decrypt2017” directly after the original file’s extension (e.g., document.docx.decrypt2017, spreadsheet.xlsx.decrypt2017, backup.zip.decrypt2017). It preserves the original filename and preceding extension untouched.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First reported to security vendors and communities in mid-April 2017, with peak infection waves observed throughout May 2017. The variant was eclipsed by larger outbreaks (e.g., WannaCry and NotPetya) later that spring, but continued to surface sporadically into Q3-2017.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Remote Desktop Protocol (RDP) brute-force attacks originating from compromised intrusion brokers—accounts/passwords harvested from previous infostealer campaigns.
  • Spear-phishing e-mails with password-protected ZIP attachments containing JS/VBS droppers that fetched the ransomware payload from hacked WordPress sites.
  • Exploitation of unpatched Apache Struts (CVE-2017-5638) and Oracle WebLogic (CVE-2017-10271) on public-facing web servers to drop the executable.
  • Watering-hole attacks leveraging cracked or pirated software sites where trojanized installers bundled the .decrypt2017 payload together with adware.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  1. Restrict RDP:
    – Disable RDP entirely if not needed.
    – If required, expose only through VPN-enforced gateways.
    – Enforce multi-factor authentication, account lockout (max 5 attempts), and strong, unique passwords.
  2. Patch aggressively: apply Windows Updates, Apache Struts patches, Oracle WebLogic critical patches, Java.
  3. E-mail hardening: deploy sandboxed attachment inspection, block executables and archives containing scripts, enable SPF/DKIM/DMARC and disable macro auto-execution in Office.
  4. Segment networks & apply least-privilege.
  5. Offline, immutable backups (3-2-1 rule) and regular restore drills.
  6. Application allow-listing (Microsoft AppLocker / Windows Defender Application Control) to stop unsigned binaries from running.
  7. EDR/NGAV with behavioral detection—ensure signature coverage for .decrypt2017 and other GlobeImposter family variants.

2. Removal

  • Infection Cleanup (step-by-step):
  1. Isolate the host: unplug NIC, disable Wi-Fi, or block MAC address at the switch.
  2. Boot into Safe Mode with Networking (or WinRE offline USB).
  3. Kill malicious processes: use tools like ESET SysRescue Live USB or Malwarebytes “Ransom.Decrypt2017.b” removal signatures. Common process names:
    • rdpfw32.exe, explorer101.exe, info.exe.
  4. Delete persistence:
    – Registry: HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\Updater
    – Scheduled Task: \Microsoft\Windows\srvcl32 pointing to %APPDATA%\[random]\svchost.exe.
  5. Scan the full disk with reputable offline scanners (Sophos, Kaspersky, Bitdefender). Allow them to quarantine infected Windows binaries (icons, executables replaced).
  6. Reboot into normal mode then run a second scan.
  7. Restore normal Windows services: check for disabled Shadow Copy services or modified bcdedit boot settings, reverse if altered.

3. File Decryption & Recovery

  • Recovery Feasibility: ✅ Some victims can achieve full decryption.
    .decrypt2017 is a strain of the GlobeImposter 2.0 family. Researchers released Emsisoft GlobeImposter Decryptor in August 2017 after exploiting a flaw in key material generation (use of static prime leading to predictable RSA public key).
  • Step-by-step decryption:

  1. Confirm your files adhere to the .decrypt2017 naming convention; other extensions from later GlobeImposter iterations may not support the tool.

  2. Copy an original unencrypted file plus its .decrypt2017 counterpart onto a safe test machine (or offline disk).

  3. Download Emsisoft Decryptor for GlobeImposter 2.0 directly from www.emsisoft.com/decrypt-globeimposter2.

  4. Run the tool with administrative rights and point it to the root directory containing encrypted data.

  5. Let the tool create the pair key; if successful, decryption will begin automatically.

  6. Important: keep backups of the encrypted files in case the decryptor fails; overwriting files is irreversible once decryption completes.

    If decryption fails, the campaign you faced belongs to a later code-drop variant—restore from offline backups instead.

4. Essential Tools / Patches

  • Microsoft Security Bulletins:
    – MS17-010 (SMBv1 patches required for a fully hardened environment)
  • Security vendor public utilities:
    – Emsisoft GlobeImposter Decryptor 2.0
    – Trend Ransomware File Decryptor (beta signatures, still lists .decrypt2017)
  • System-hardening scripts:
    – NIST CIS Windows 10/11 Benchmarks
    – Microsoft Defender ASR rules: “Block process creations originating from PSExec and WMI commands” (preemptive RDP lateral movement).
  • Backup software: Veeam Immutable Backups (Linux hardened repository), AWS S3 “Object Lock” snapshots.

5. Other Critical Information

  • Unique Characteristics that differentiate it:

  • .decrypt2017 does not delete shadow copies in most observed samples; vssadmin list shadows may still contain recovery points.

  • Uses double-extension trick to evade basic filters (e.g., when e-mail MTAs strip known bad extensions).

  • Delivery binaries frequently self-signed with expired certificates to reduce AV suspicion.

  • Drops a ransom note named HowToBackFiles.txt in every affected folder with BTC wallet 1E…xY (average ransom demand 0.20–0.30 BTC at 2017 value).

  • Broader Impact:

  • Primarily impacted small to medium municipalities and healthcare orgs lacking managed SOC capability.

  • Demonstrated how diverting from mass exploits (like EternalBlue) toward targeted RDP compromise could still yield significant ransoms yet remain under the radar for weeks.

  • Served as a pivot point for red-team exercises to pressure, successfully, many orgs into finally closing SMBv1 and RDP blast radius.