Detection: ESXi Syslog Config Change

Updated Date: 2025-05-13 ID: e530beb9-9b8c-4c9b-9776-0a05521ff32d Author: Raven Tait, Splunk Type: TTP Product: Splunk Enterprise Security

Description

This detection identifies changes to the syslog configuration on an ESXi host using esxcli, which may indicate an attempt to disrupt log collection and evade detection.

Search

1`esxi_syslog` Message="*syslog config set*" AND Message="*esxcli*" 
2| rex field=_raw "\].*\[\s*(?P<user>[^\]]+)\]:\s(?P<command>.+)" 
3| rex field=_raw "Z (?<dest>[\w\.]+)\s" 
4| stats min(_time) as firstTime max(_time) as lastTime count by dest user command 
5| `security_content_ctime(firstTime)` 
6| `security_content_ctime(lastTime)` 
7| `esxi_syslog_config_change_filter`

Data Source

Name	Platform	Sourcetype	Source
VMWare ESXi Syslog	N/A	`'vmw-syslog'`	`'vmware:esxlog'`

Macros Used

Name	Value
esxi_syslog	`sourcetype=vmw-syslog OR sourcetype=vmware:esxlog*`
esxi_syslog_config_change_filter	`search *`

esxi_syslog_config_change_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1562.003	Impair Command History Logging	Defense Evasion

Exploitation

DE.CM

CIS 10

Sea Turtle

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

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

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

Syslog config was modified on ESXi host $dest$.

Risk Object	Risk Object Type	Risk Score	Threat Objects
dest	system	60	No Threat Objects

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`vmware:esxlog`	`vmw-syslog`
Integration	✅ Passing	Dataset	`vmware:esxlog`	`vmw-syslog`

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 1