THEGENTLEMEN Ransomware Gang: 23 New Victims Posted — Sector Targeting Analysis & Detection Rules

---
id: a1b2c3d4-e5f6-4a5b-8c9d-0e1f2a3b4c5d
level: critical
title: Potential Cisco FMC Deserialization Exploit CVE-2026-20131
description: Detects potential exploitation of Cisco Secure Firewall Management Center deserialization vulnerability via suspicious URI patterns or high-volume POST requests to management endpoints.
references:
    - https://cisa.gov/known-exploited-vulnerabilities-catalog
author: Security Arsenal
date: 2026/04/20
tags:
    - attack.initial_access
    - cve.2026.20131
    - ransomware.thegentlemen
logsource:
    category: webserver
detection:
    selection:
        cs-method|contains: 'POST'
        cs-uri-query|contains:
            - '/fmc_config/'
            - '/api/fmc_config/'
    condition: selection
falsepositives:
    - Administrative configuration updates
---
id: b2c3d4e5-f6a7-5b6c-9d0e-1f2a3b4c5d6e
level: high
title: SmarterMail Authentication Bypass CVE-2026-23760
description: Detects signs of authentication bypass in SmarterMail, characterized by access to specific password reset or login paths without preceding authentication requests or with unusual user agents.
references:
    - https://cisa.gov/known-exploited-vulnerabilities-catalog
author: Security Arsenal
date: 2026/04/20
tags:
    - attack.initial_access
    - cve.2026.23760
    - ransomware.thegentlemen
logsource:
    category: webserver
detection:
    selection_uri:
        cs-uri-stem|contains:
            - '/event.aspx'
            - '/Login.aspx'
            - '/default.aspx'
    selection_suspicious:
        cs-user-agent|contains:
            - 'python-requests'
            - 'curl'
    filter_legit:
        cs-user-agent|contains: 'Mozilla'
    condition: selection_uri and selection_suspicious and not filter_legit
falsepositives:
    - Legitimate API testing
---
id: c3d4e5f6-a7b8-6c7d-0e1f-2a3b4c5d6e7f
level: high
title: Lateral Movement via PsExec and WMI Common in RaaS
description: Detects the use of PsExec or WMI for lateral movement, a common TTP for THEGENTLEMEN affiliates after gaining initial access via VPN exploits.
references:
    - https://attack.mitre.org/techniques/T1021/002/
author: Security Arsenal
date: 2026/04/20
tags:
    - attack.lateral_movement
    - attack.execution
    - ransomware.thegentlemen
logsource:
    category: process_creation
    product: windows
detection:
    selection_psexec:
        Image|endswith:
            - '\psexec.exe'
            - '\psexec64.exe'
        CommandLine|contains: '-accepteula'
    selection_wmi:
        Image|endswith:
            - '\wmic.exe'
            - '\wbem\wbemtest.exe'
        CommandLine|contains:
            - 'node:'
            - '/node:'
            - 'call process create'
    condition: 1 of selection_*
falsepositives:
    - System administration

// Hunt for lateral movement and data staging associated with THEGENTLEMEN
// Looks for rapid file creation (zip/7z/rar) and PsExec/WMI usage within short timeframes
let TimeFrame = 1h;
DeviceProcessEvents
| where Timestamp > ago(TimeFrame)
| where FileName in~ ("psexec.exe", "psexec64.exe", "wmic.exe", "powershell.exe")
| where ProcessCommandLine has_any ("-accepteula", "/node:", "Compress-Archive", "Invoke-RestMethod")
| project Timestamp, DeviceName, FileName, ProcessCommandLine, InitiatingProcessAccountName
| join (
    DeviceFileEvents
    | where Timestamp > ago(TimeFrame)
    | where FolderPath contains "\\" and (FileName endswith ".zip" or FileName endswith ".rar" or FileName endswith ".7z")
    | project Timestamp, DeviceName, FileName, FolderPath
) on DeviceName
| summarize ActivityCount = count(), Timestamp = max(Timestamp) by DeviceName, InitiatingProcessAccountName, FileName
| order by ActivityCount desc

# THEGENTLEMEN Response Script: Check for VSS Manipulation and Scheduled Task Persistence
# Run with Administrative Privileges

Write-Host "[*] Starting THEGENTLEMEN Indication of Compromise Check..." -ForegroundColor Cyan

# 1. Check for Volume Shadow Copy Deletion Attempts (Common Pre-Encryption)
Write-Host "[+] Checking for VSSAdmin deletion events in Security Log (Requires Auditing)..." -ForegroundColor Yellow
try {
    $vssEvents = Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4674; StartTime=(Get-Date).AddHours(-24)} -ErrorAction SilentlyContinue
    if ($vssEvents) {
        $vssSuspicious = $vssEvents | Where-Object { $_.Message -match 'vssadmin' -and $_.Message -match 'delete' }
        if ($vssSuspicious) {
            Write-Host "[!] CRITICAL: VSS Admin deletion commands detected." -ForegroundColor Red
            $vssSuspicious | Select-Object TimeCreated, Message | Format-List
        } else {
            Write-Host "[-] No VSS deletion events found." -ForegroundColor Green
        }
    }
} catch {
    Write-Host "[-] Could not read Security Logs or Auditing not enabled." -ForegroundColor Gray
}

# 2. Enumerate Scheduled Tasks created in the last 7 days
Write-Host "[+] Checking for Scheduled Tasks created/modified in last 7 days..." -ForegroundColor Yellow
$suspiciousTasks = Get-ScheduledTask | Where-Object { $_.Date -gt (Get-Date).AddDays(-7) }
if ($suspiciousTasks) {
    Write-Host "[!] WARNING: Recently created/modified tasks found:" -ForegroundColor Red
    $suspiciousTasks | Select-Object TaskName, Date, Author, TaskPath | Format-Table
} else {
    Write-Host "[-] No recent suspicious scheduled tasks." -ForegroundColor Green
}

Write-Host "[*] Check complete." -ForegroundColor Cyan


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