Detection rules › Splunk
ESXi Encryption Settings Modified
Detects the disabling of critical encryption enforcement settings on an ESXi host, such as secure boot or executable verification requirements, which may indicate an attempt to weaken hypervisor integrity or allow unauthorized code execution.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Defense Impairment | T1685 Disable or Modify Tools |
Rule body splunk
name: ESXi Encryption Settings Modified
id: dbbbe26f-83fe-4ee3-8b77-ccf7fbd416c8
version: 5
creation_date: '2025-07-11'
modification_date: '2026-05-13'
author: Raven Tait, Splunk
status: production
type: TTP
description: Detects the disabling of critical encryption enforcement settings on an ESXi host, such as secure boot or executable verification requirements, which may indicate an attempt to weaken hypervisor integrity or allow unauthorized code execution.
data_source:
- VMWare ESXi Syslog
search: '`esxi_syslog` Message="*system settings encryption set*" NOT Message="*shell.*" Message IN ("* -s *", "* -e *","*--require-secure-boot*", "*require-exec-installed-only*", "execInstalledOnly") | rex field=_raw "Z (?<dest>[\w\.]*)\s.*\]: \[(?<user>\w+)\]:(?<command>.+)" | stats min(_time) as firstTime max(_time) as lastTime count by dest user command | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `esxi_encryption_settings_modified_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 ("$dest$") | 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: 7d
latest_offset: "0"
finding:
title: Encryption settings modified on ESXi host $dest$.
entity:
field: dest
type: system
score: 50
analytic_story:
- ESXi Post Compromise
- Black Basta Ransomware
asset_type: Infrastructure
mitre_attack_id:
- T1685
product:
- Splunk Enterprise
- Splunk Enterprise Security
- Splunk Cloud
category: application
security_domain: endpoint
tests:
- name: True Positive Test
attack_data:
- data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1562/esxi_encryption_modified/esxi_encryption_modified.log
source: vmware:esxlog
sourcetype: vmw-syslog
test_type: unit
Stages and Predicates
Stage 1: search
`esxi_syslog` Message="*system settings encryption set*" NOT Message="*shell.*" Message IN ("* -s *", "* -e *","*--require-secure-boot*", "*require-exec-installed-only*", "execInstalledOnly")
Stage 2: rex
| rex field=_raw "Z (?<dest>[\w\.]*)\s.*\]: \[(?<user>\w+)\]:(?<command>.+)"
Stage 3: stats
| stats min(_time) as firstTime max(_time) as lastTime count by dest user command
Stage 4: search
| `security_content_ctime(firstTime)`
Stage 5: search
| `security_content_ctime(lastTime)`
Stage 6: search
| `esxi_encryption_settings_modified_filter`
Exclusions
Top-level NOT(...) conjuncts: predicates this rule actively suppresses.
| Field | Kind | Excluded values |
|---|---|---|
Message | eq | "*shell.*" |
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.
| Field | Kind | Values |
|---|---|---|
Message | eq |
|
Message | in |
|
sourcetype | in |
|