title: Potential Exploitation CVE-2026-20131 Cisco FMC Deserialization
description: Detects potential exploitation attempts of Cisco Secure Firewall Management Center deserialization vulnerability via suspicious HTTP POST patterns.
status: experimental
date: 2026/04/20
references:
    - https://www.cisa.gov/known-exploited-vulnerabilities-catalog
author: Security Arsenal Research
logsource:
    category: webserver
detection:
    selection:
        c-uri|contains: '/fsapi/log/upload'
        cs-method: 'POST'
    condition: selection
falsepositives:
    - Legitimate administrative file uploads
level: critical

title: SmarterMail Authentication Bypass CVE-2026-23760
description: Detects potential authentication bypass attempts on SmarterMail servers via alternate path traversal.
status: experimental
date: 2026/04/20
references:
    - https://www.cisa.gov/known-exploited-vulnerabilities-catalog
author: Security Arsenal Research
logsource:
    category: webserver
detection:
    selection:
        c-uri|contains:
            - '/LiveApp/'
            - '/aspx/'
        cs-method: 'GET'
    filter:
        cs-user-agent|re: 'SmarterTools*'
    condition: selection and not filter
falsepositives:
    - Administrative interface access
level: high

title: Ransomware Behavior - Volume Shadow Copy Deletion via VssAdmin
description: Detects commands used to delete Volume Shadow Copies, a common precursor to encryption by THEGENTLEMEN and similar groups.
status: experimental
date: 2026/04/20
author: Security Arsenal Research
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\vssadmin.exe'
            - '\wmic.exe'
        CommandLine|contains:
            - 'delete shadows'
            - 'shadowcopy delete'
    condition: selection
falsepositives:
    - Legitimate system administration (rare)
level: critical

// Hunt for lateral movement and staging associated with THEGENTLEMEN
// Focuses on PsExec, WMI, and unusual administrative activity
DeviceProcessEvents
| where Timestamp > ago(7d)
| where InitiatingProcessAccountName != "System"
| where (FileName in~ ("psexec.exe", "psexec64.exe") 
    or ProcessCommandLine has_any ("wmic", "powershell.exe -enc", "-encodedcommand") 
    or FileName in~ ("wmiexec.exe", "wmiprvse.exe"))
| summarize Count = count(), DistinctDevices = dcount(DeviceId), ArgList = make_set(ProcessCommandLine) by DeviceName, AccountName, FileName
| where Count > 2
| extend Severity = iif(FileName contains "psexec", "High", "Medium")
| order by Count desc

<#
.SYNOPSIS
    Checks for indicators of ransomware staging (Shadow Copy manipulation and recent Scheduled Tasks).
    Recommended to run on all endpoints if THEGENTLEMEN activity is suspected.
#>

Write-Host "Checking THEGENTLEMEN Indicators of Compromise..." -ForegroundColor Yellow

# 1. Check for recent scheduled tasks (Persistence)
$suspiciousTasks = Get-ScheduledTask | Where-Object {$_.Date -gt (Get-Date).AddDays(-7)} | Select-Object TaskName, Date, Author, Actions
if ($suspiciousTasks) {
    Write-Host "[ALERT] Suspicious Scheduled Tasks created in last 7 days:" -ForegroundColor Red
    $suspiciousTasks | Format-Table -AutoSize
} else {
    Write-Host "[OK] No suspicious recent scheduled tasks found." -ForegroundColor Green
}

# 2. Check Volume Shadow Copy Status (Staging)
$vssStatus = vssadmin list shadows
if ($vssStatus -match "No shadow copies found") {
    Write-Host "[WARNING] No shadow copies exist. System may be vulnerable to immediate data loss." -ForegroundColor Cyan
} else {
    Write-Host "[OK] Shadow copies are present." -ForegroundColor Green
}

# 3. Check for unusual RDP/VPN sessions (Optional)
$rdpUsers = query user | Select-String -Pattern "Active"
Write-Host "Active Sessions: `n $rdpUsers"


---

# Incident Response Priorities

**T-Minus Detection Checklist (Before Encryption):**
1.  **Cisco FMC Logs:** Immediate review of firewall management center logs for `/fsapi/log/upload` anomalies.
2.  **SmarterMail Logs:** Audit email server logs for successful authentications from unfamiliar IPs.
3.  **PsExec/WMI:** Hunt for `psexec` execution across the environment—a hallmark of their lateral movement.

**Critical Assets for Exfiltration:**
*   **Business Services:** Client PII and contract databases.
*   **Manufacturing:** CAD drawings and intellectual property.
*   **Healthcare:** Patient medical records (PHI).

**Containment Actions (Ordered by Urgency):**
1.  **Isolate:** Disconnect infected or suspected hosts from the network immediately; do not shut down (preserve RAM).
2.  **Reset:** Revoke all credentials for local admins and service accounts on affected segments.
3.  **Block:** Block inbound traffic to SmarterMail and Cisco FMC interfaces from non-corporate IP ranges.

---

# Hardening Recommendations

**Immediate (Within 24 Hours):**
*   **Patch:** Apply the patch for **CVE-2026-20131** (Cisco FMC) and **CVE-2026-23760** (SmarterMail) immediately. If patching is delayed, place these management interfaces behind a zero-trust VPN with MFA, not exposed directly to the internet.
*   **Disable:** Disable `vssadmin.exe` for non-admin users via GPO to hinder data wiping.

**Short-Term (2 Weeks):**
*   **Architecture:** Implement a secure access gateway for all management planes (Firewall, Email, Backup). No direct internet-accessible management IPs.
*   **Segmentation:** Enforce strict micro-segmentation between the IT network and OT/Manufacturing networks to prevent lateral movement from compromised business workstations.

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