Cookeville Regional Breach: Detecting and Containing Encryption-Based Healthcare Ransomware

---
title: Potential Ransomware Activity - Volume Shadow Copy Deletion
id: 4f326b2e-2e6f-4e6c-9f3a-2b5a5c9d8e7f
status: experimental
description: Detects attempts to delete Volume Shadow Copies, a common tactic used by ransomware to prevent data recovery. This technique often utilizes vssadmin, wbadmin, or PowerShell.
references:
  - https://attack.mitre.org/techniques/T1490/
author: Security Arsenal
date: 2025/04/10
tags:
  - attack.impact
  - attack.t1490
logsource:
  category: process_creation
  product: windows
detection:
  selection_vssadmin:
    Image|endswith: '\vssadmin.exe'
    CommandLine|contains: 'delete shadows'
  selection_wbadmin:
    Image|endswith: '\wbadmin.exe'
    CommandLine|contains: 'delete catalog'
  selection_powershell:
    Image|endswith: '\powershell.exe'
    CommandLine|contains:
      - 'Remove-ItemProperty'
      - 'HKLM:\\Software\\Microsoft\\Windows NT\\CurrentVersion\\Windows\\AppInit_DLLs'
  condition: 1 of selection_*
falsepositives:
  - System administrators performing maintenance
level: high
---
title: Mass File Encryption via Cipher
id: 5a2b1c9d-8f3e-4a1b-9c7d-1e2f3a4b5c6d
status: experimental
description: Detects the use of cipher.exe to encrypt or overwrite data on multiple drives, a behavior consistent with wiper or ransomware payloads.
references:
  - https://attack.mitre.org/techniques/T1485/
author: Security Arsenal
date: 2025/04/10
tags:
  - attack.impact
  - attack.t1485
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    Image|endswith: '\cipher.exe'
    CommandLine|contains: '/w'
  condition: selection
falsepositives:
  - Rare administrative disk cleaning tasks
level: high
---
title: Suspicious PowerShell Encoded Command Execution
id: 7b3c2d1e-0a4f-5b2c-8d9e-3f4a5b6c7d8e
status: experimental
description: Detects base64 encoded commands in PowerShell, frequently used to obfuscate ransomware download and execution logic.
references:
  - https://attack.mitre.org/techniques/T1059/001/
author: Security Arsenal
date: 2025/04/10
tags:
  - attack.execution
  - attack.t1059.001
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    Image|endswith: '\powershell.exe'
    CommandLine|contains:
      - 'FromBase64String'
      - 'EncodedCommand'
      - '-enc'
  condition: selection
falsepositives:
  - Legitimate software deployment scripts
level: medium

// Hunt for suspicious process executions related to ransomware precursors
DeviceProcessEvents
| where Timestamp > ago(7d)
| where FileName in~ ('vssadmin.exe', 'wbadmin.exe', 'cipher.exe', 'bcdedit.exe')
| where ProcessCommandLine has_any ('delete', 'shadow', 'recoveryenabled', 'quiet')
| project Timestamp, DeviceName, InitiatingProcessFileName, FileName, ProcessCommandLine, AccountName
| order by Timestamp desc

// Hunt for mass file modifications (potential encryption)
DeviceFileEvents
| where Timestamp > ago(1d)
| where ActionType in ('FileCreated', 'FileModified')
| summarize count() by FileName, DeviceName, bin(Timestamp, 5m)
| where count_ > 50 // Threshold for mass modification
| join kind=inner (DeviceProcessEvents) on DeviceName
| project Timestamp, DeviceName, FileName, InitiatingProcessFileName, InitiatingProcessCommandLine, count_

-- Hunt for processes interacting with Windows Shadow Copies or Encryption
SELECT Pid, Name, CommandLine, Exe, Username, CreateTime
FROM pslist()
WHERE Name =~ 'vssadmin'
   OR Name =~ 'wbadmin'
   OR Name =~ 'cipher'
   OR CommandLine =~ '/w'
   OR CommandLine =~ 'delete shadows'

-- Check for recently modified files with common ransomware extensions
SELECT FullPath, Size, Mtime, Mode
FROM glob(globs='/*', root=WindowsDrives)
WHERE Mtime > now() - 1h
   AND FullPath =~ '\.(locked|encrypted|crypt|locked\.[a-z]+)$'

<#
.SYNOPSIS
    Healthcare Ransomware Hardening & Remediation Script
.DESCRIPTION
    Disables common attack vectors, audits suspicious services, and ensures key recovery protection mechanisms are active.
#>

Write-Host "[+] Starting Healthcare Environment Hardening..." -ForegroundColor Cyan

# 1. Disable SMBv1 (Common lateral movement vector)
Write-Host "[+] Disabling SMBv1 Protocol..." -ForegroundColor Yellow
Set-SmbServerConfiguration -EnableSMB1Protocol $false -Force

# 2. Disable WebClient/WinRM (often used for lateral movement)
Write-Host "[+] Disabling WebClient Service..." -ForegroundColor Yellow
Set-Service -Name WebClient -StartupType Disabled -ErrorAction SilentlyContinue
Stop-Service -Name WebClient -Force -ErrorAction SilentlyContinue

# 3. Ensure Volume Shadow Copy Service (VSS) is running (if not impacted)
Write-Host "[+] Checking VSS Service Status..." -ForegroundColor Yellow
$vss = Get-Service -Name VSS -ErrorAction SilentlyContinue
if ($vss.Status -ne 'Running') {
    try {
        Start-Service -Name VSS -ErrorAction Stop
        Write-Host "    VSS Service Started Successfully." -ForegroundColor Green
    } catch {
        Write-Host "    Failed to start VSS: $_" -ForegroundColor Red
    }
} else {
    Write-Host "    VSS Service is Running." -ForegroundColor Green
}

# 4. Audit Local Administrators for suspicious accounts
Write-Host "[+] Auditing Local Administrators Group..." -ForegroundColor Yellow
Get-LocalGroupMember -Group "Administrators" | Format-Table Name, SID, PrincipalSource

Write-Host "[+] Hardening Script Completed." -ForegroundColor Cyan
Write-Host "[!] IMMEDIATE ACTION: Revoke all credentials used in the last 48 hours and rotate VPN/RDP passwords." -ForegroundColor Red