splunk_escuTTP

ESXi Firewall Disabled

This detection identifies when the ESXi firewall is disabled or set to permissive mode, which can expose the host to unauthorized access and network-based attacks. Such changes are often a precursor to lateral movement, data exfiltration, or the installation of malicious software by a threat actor.

MITRE ATT&CK

T1562.004

Detection Query

`esxi_syslog` Message="*network firewall set*" AND Message="*enabled f*" | rex field=_raw "Z (?<dest>[\w\.]+)\s" | stats min(_time) as firstTime max(_time) as lastTime count by dest Message | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `esxi_firewall_disabled_filter`

Author

Raven Tait, Splunk

Created

2026-03-10

Data Sources

VMWare ESXi Syslog

Tags

ESXi Post CompromiseBlack Basta RansomwareChina-Nexus Threat Activity

Raw Content

name: ESXi Firewall Disabled
id: e321804c-8eb5-42f2-a843-36b289a6c6b2
version: 3
date: '2026-03-10'
author: Raven Tait, Splunk
status: production
type: TTP
description: This detection identifies when the ESXi firewall is disabled or set to permissive mode, which can expose the host to unauthorized access and network-based attacks. Such changes are often a precursor to lateral movement, data exfiltration, or the installation of malicious software by a threat actor.
data_source:
    - VMWare ESXi Syslog
search: '`esxi_syslog` Message="*network firewall set*" AND Message="*enabled f*" | rex field=_raw "Z (?<dest>[\w\.]+)\s" | stats min(_time) as firstTime max(_time) as lastTime count by dest Message | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `esxi_firewall_disabled_filter`'
how_to_implement: This is based on syslog data generated by VMware ESXi hosts. To implement this search, you must configure your ESXi systems to forward syslog output to your Splunk deployment. These logs must be ingested with the appropriate Splunk Technology Add-on for VMware ESXi Logs, which provides field extractions and CIM compatibility.
known_false_positives: Limited false positives in most environments, however tune as needed.
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search  dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") starthoursago=168  | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: Firewall disabled on ESXi host $dest$.
    risk_objects:
        - field: dest
          type: system
          score: 50
    threat_objects: []
tags:
    analytic_story:
        - ESXi Post Compromise
        - Black Basta Ransomware
        - China-Nexus Threat Activity
    asset_type: Infrastructure
    mitre_attack_id:
        - T1562.004
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1562.004/esxi_firewall_disabled/esxi_firewall_disabled.log
          source: vmware:esxlog
          sourcetype: vmw-syslog