Signature Healthcare Cyberattack: Analyzing Ransomware Impact on Clinical Operations and ER Diversion

---
title: Potential Ransomware Shadow Copy Deletion
id: 550d9a23-0f72-4e3a-a8c5-1d2f3b4c5d6e
status: experimental
description: Detects attempts to delete volume shadow copies using vssadmin or wmic, a common tactic used by ransomware to prevent recovery.
references:
  - https://attack.mitre.org/techniques/T1490/
author: Security Arsenal
date: 2026/04/06
tags:
  - attack.impact
  - attack.t1490
logsource:
  category: process_creation
  product: windows
detection:
  selection_vssadmin:
    Image|endswith: '\vssadmin.exe'
    CommandLine|contains: 'delete shadows'
  selection_wmic:
    Image|endswith: '\wmic.exe'
    CommandLine|contains: 'shadowcopy delete'
  condition: 1 of selection*
falsepositives:
  - Legitimate system administration (rare in production EHR environments)
level: critical
---
title: Potential Ransom Note Creation on Desktop
id: 7a3f1c82-9e4b-4d67-bc12-3e5a8f901234
status: experimental
description: Detects the creation of text or HTML files on the Desktop with keywords often found in ransom notes (e.g., README, RESTORE, DECRYPT).
references:
  - https://attack.mitre.org/techniques/T1485/
author: Security Arsenal
date: 2026/04/06
tags:
  - attack.impact
  - attack.t1485
logsource:
  category: file_create
  product: windows
detection:
  selection:
    TargetFilename|contains: '\Desktop\'
    TargetFilename|endswith:
      - '.txt'
      - '.html'
  keywords:
    TargetFilename|contains:
      - 'README'
      - 'RECOVER'
      - 'RESTORE'
      - 'DECRYPT'
      - 'INSTRUCTIONS'
  condition: selection and keywords
falsepositives:
  - User-created text files
level: high
---
title: Suspicious PowerShell Encoded Payload
id: 8b2e0d93-1f5c-5e78-dc23-4f6b9g012345
status: experimental
description: Detects PowerShell execution with encoded commands, frequently used to obfuscate malicious payloads in ransomware attacks.
references:
  - https://attack.mitre.org/techniques/T1059/001/
author: Security Arsenal
date: 2026/04/06
tags:
  - attack.execution
  - attack.t1059.001
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    Image|endswith:
      - '\powershell.exe'
      - '\pwsh.exe'
    CommandLine|contains:
      - ' -enc '
      - ' -EncodedCommand '
  filter:
    CommandLine|contains: 'ManagedScheduledTask' # Common false positive in mgmt
  condition: selection and not filter
falsepositives:
  - Legitimate administrative scripts
level: medium

// Hunt for processes manipulating VSS shadows or common ransomware utilities
DeviceProcessEvents
| where Timestamp > ago(1d)
| where (FileName in~ ("vssadmin.exe", "wmic.exe", "bcdedit.exe", "wbadmin.exe") 
        or ProcessCommandLine has_any ("delete shadows", "shadowcopy delete", "recoveryenabled no", "delete catalog"))
| extend HostName = DeviceName, Account = AccountName, InitiatingProcess = InitiatingProcessFileName
| project Timestamp, HostName, Account, FileName, ProcessCommandLine, InitiatingProcessFolderPath, InitiatingProcessCommandLine
| order by Timestamp desc

-- Hunt for suspicious process execution related to ransomware impact
SELECT Pid, Name, CommandLine, Exe, Username, CreateTime
FROM pslist()
WHERE Name =~ 'vssadmin.exe' 
   OR Name =~ 'wbadmin.exe'
   OR (Name =~ 'powershell.exe' AND CommandLine =~ '-enc')
   OR Name =~ 'taskkill.exe' -- Often used to kill AV/EDR

# Script to Audit RDP Exposure and Local Admin Members (Common Lateral Movement Vectors)
# Run this on critical clinical workstations and servers to audit security posture.

function Invoke-HealthcareRansomwareAudit {
    Write-Host "Starting Healthcare Security Audit..." -ForegroundColor Cyan

    # Check for RDP Enabled
    $RDPStatus = (Get-ItemProperty "HKLM:\SYSTEM\CurrentControlSet\Control\Terminal Server").fDenyTSConnections
    if ($RDPStatus -eq 0) {
        Write-Host "[WARNING] RDP is ENABLED on this host." -ForegroundColor Red
    } else {
        Write-Host "[INFO] RDP is disabled." -ForegroundColor Green
    }

    # Check Local Administrators Group for suspicious accounts
    $AdminGroupMembers = Get-LocalGroupMember -Group "Administrators" -ErrorAction SilentlyContinue
    $SuspiciousPattern = ".*admin.*|.*backup.*|.*service.*"
    
    Write-Host "\nAuditing Local Administrators Group:" -ForegroundColor Cyan
    foreach ($Member in $AdminGroupMembers) {
        if ($Member.Name -match "S-1-5-21-" + ".*500" -or $Member.Name -notmatch "Domain Admins" -and $Member.Name -notmatch "Enterprise Admins") {
            Write-Host "[ALERT] Unusual Admin Member found: $($Member.Name) (Source: $($Member.SID))" -ForegroundColor Yellow
        }
    }

    # Check for Shadow Copy Deletion Events (System Event Log 5105 or similar, simplified check)
    Write-Host "\nChecking Event Logs for VSS Admin Operations..." -ForegroundColor Cyan
    $VSSAudit = Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4672; StartTime=(Get-Date).AddHours(-24)} -ErrorAction SilentlyContinue | 
                 Where-Object { $_.Message -match 'vssadmin' -or $_.Message -match 'wmic' }
    if ($VSSAudit) {
        Write-Host "[CRITICAL] Found recent VSS/WMIC execution by privileged accounts." -ForegroundColor Red
    } else {
        Write-Host "[INFO] No immediate VSS manipulation events found in last 24h." -ForegroundColor Green
    }
}

Invoke-HealthcareRansomwareAudit