Caribbean Medical Center Encryption Incident: Ransomware Detection and IR Playbook

Introduction

A recent encryption-based cyber incident targeting Hospital Caribbean Medical Center in Puerto Rico has compromised the protected health information (PHI) of approximately 92,000 individuals. The attack, discovered to have occurred between March 10 and March 12, involved unauthorized network access that led to the encryption of files on the hospital's systems. For defenders, this is a critical reminder of the severity of ransomware in the healthcare sector. The encryption of medical records isn't just a data breach; it is a direct threat to patient safety and operational continuity. Immediate action is required to detect similar encryption behaviors and ensure robust backup isolation.

Technical Analysis

Attack Overview

The incident is described as an "encryption-based cyber incident," which strongly indicates a ransomware-style attack utilizing asymmetric cryptography to lock files. While the specific malware strain (e.g., LockBit, Conti, or Ryuk) was not immediately disclosed in the breach notification, the tactic, technique, and procedure (TTP) follows the standard MITRE ATT&CK framework for Impact: Data Encrypted for Impact (T1486).

Exploitation and Mechanics

In these incidents, threat actors typically gain initial access via:

1. Phishing: Credential harvesting leading to initial access.
2. Exploited Public-Facing Application: Vulnerabilities in VPNs or RDP services.
3. Lateral Movement: Use of SMB/WinRM or remote desktop tools to spread to file servers.

Once inside, the attack chain proceeds to:

• Privilege Escalation: Dumping credentials (LSASS memory) or exploiting vulnerabilities to gain Admin rights.
• Defense Evasion: Disabling antivirus or security logging.
• Impact: Execution of the encryption payload.

The encryption process targets common productivity and database files (.docx, .pdf, .db, .bak). A key precursor observed in 90% of ransomware cases is the deletion of Volume Shadow Copies to prevent easy recovery, often executed via vssadmin.exe or wmic.exe.

Exploitation Status

This is a Confirmed Active Exploitation scenario. The hospital has confirmed the encryption of files and the exfiltration or access of sensitive data.

Detection & Response

The following detection rules focus on the precursor behaviors common to encryption-based attacks, specifically targeting the destruction of recovery mechanisms (Volume Shadow Copies) and the mass execution of encryption utilities.

---
title: Potential Ransomware Activity - Volume 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 precursor to ransomware execution to prevent file recovery.
references:
  - https://attack.mitre.org/techniques/T1490/
author: Security Arsenal
date: 2025/04/01
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:
  - System administrators manually managing storage (rare in production envs)
level: critical
---
title: Suspicious Mass Encryption via Cipher Utility
id: 7a3f1c82-9e4b-4d67-bc12-3e5a8f901234
status: experimental
description: Detects the use of cipher.exe to wipe data or overwrite deleted files, often used by ransomware to ensure data cannot be recovered.
references:
  - https://attack.mitre.org/techniques/T1486/
author: Security Arsenal
date: 2025/04/01
tags:
  - attack.impact
  - attack.t1486
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    Image|endswith: '\cipher.exe'
    CommandLine|contains: '/w'
  condition: selection
falsepositives:
  - Legitimate disk wiping procedures by IT staff
level: high

KQL (Microsoft Sentinel / Defender)

This query hunts for the deletion of shadow copies and abnormal process execution patterns associated with ransomware deployment.

DeviceProcessEvents
| where Timestamp > ago(7d)
| where (FileName in~ ("vssadmin.exe", "wmic.exe") and ProcessCommandLine has_any ("delete", "shadowcopy"))
   or (FileName == "cipher.exe" and ProcessCommandLine has "/w")
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine, InitiatingProcessFileName
| order by Timestamp desc

Velociraptor VQL

This artifact hunts for processes that are commonly abused to disable system recovery or perform encryption, focusing on command-line arguments.

-- Hunt for ransomware precursor processes
SELECT Pid, Name, CommandLine, Exe, Username, CreateTime
FROM pslist()
WHERE Name =~ 'vssadmin'
   AND CommandLine =~ 'delete'
   OR Name =~ 'wmic'
   AND CommandLine =~ 'shadowcopy'
   OR Name =~ 'cipher'
   AND CommandLine =~ '/w'

Remediation Script (PowerShell)

Use this script to verify the status of the Volume Shadow Copy Service (VSS) and ensure no recent shadow copies were maliciously deleted. It also checks for the presence of common ransomware note extensions.

# Remediation and Verification Script
Write-Host "Checking VSS Service Status..."
$vssService = Get-Service -Name VSS -ErrorAction SilentlyContinue
if ($vssService.Status -ne 'Running') {
    Write-Host "[WARNING] VSS Service is not running. Attempting to start..." -ForegroundColor Yellow
    Start-Service -Name VSS
} else {
    Write-Host "[INFO] VSS Service is running." -ForegroundColor Green
}

# Check for recent Shadow Copy deletions in Event Log
Write-Host "Checking Event Logs for VSS Deletion events..."
$vssEvents = Get-WinEvent -FilterHashtable @{LogName='Application'; ProviderName='VSS'; ID=12343} -MaxEvents 10 -ErrorAction SilentlyContinue
if ($vssEvents) {
    Write-Host "[ALERT] Found recent Shadow Copy Deletion events:" -ForegroundColor Red
    $vssEvents | Select-Object TimeCreated, Message | Format-List
} else {
    Write-Host "[INFO] No immediate VSS deletion events found in Application Log." -ForegroundColor Green
}

# Check for common ransomware note files
Write-Host "Scanning user profiles for ransomware notes..."
$paths = @("C:\Users\", "C:\Documents and Settings\")
$extensions = @("*.encrypted", "*.locky", "*.zepto", "*README*.txt", "*RECOVER*.txt")
foreach ($path in $paths) {
    if (Test-Path $path) {
        Get-ChildItem -Path $path -Recurse -Include $extensions -ErrorAction SilentlyContinue | ForEach-Object {
            Write-Host "[SUSPICIOUS] Found potential ransom note: $($_.FullName)" -ForegroundColor Red
        }
    }
}

Remediation

1. Immediate Isolation: Immediately isolate affected systems (clinical workstations, file servers) from the network. Pull the Ethernet cable or disable Wi-Fi adapters via Switch/Router ACLs to prevent lateral movement.
2. Preservation: Do not reboot or power off servers if possible; acquire a forensic memory image first. If volatile data must be lost, prioritize the preservation of disk images via block-level hashing.
3. Credential Reset: Assume Active Directory compromise. Force a password reset for all privileged accounts (Domain Admins) and any service accounts identified in the logs.
4. Data Recovery: Restore encrypted data from offline backups. Do not connect backup drives to the infected network until sanitization is complete. Ensure backups are free of the malware payload before restoration.
5. Breach Notification: Engage legal counsel to ensure compliance with HIPAA Breach Notification Rule (45 CFR § 164.400). Notification to HHS and affected individuals (up to 92k in this case) is required within 60 days of discovery.

Related Resources

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