Detection: ESXi SSH Enabled

Updated Date: 2025-05-12 ID: b8003567-c5b6-445b-8966-ecdacc81c24d Author: Raven Tait, Splunk Type: TTP Product: Splunk Enterprise Security

Description

This detection identifies SSH being enabled on ESXi hosts, which can be an early indicator of malicious activity. Threat actors often use SSH to gain persistent remote access after compromising credentials or exploiting vulnerabilities.

Search

1`esxi_syslog` Message="*SSH access has been enabled" 
2| rex field=_raw "Z (?<dest>[\w\.]+)\s" 
3| stats min(_time) as firstTime max(_time) as lastTime count by dest Message 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `esxi_ssh_enabled_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_ssh_enabled_filter	`search *`

esxi_ssh_enabled_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
T1021.004	SSH	Lateral Movement

Exploitation

DE.CM

CIS 10

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. Some Administrators may use SSH for troubleshooting.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

SSH was enabled on ESXi host $dest$.

Risk Object	Risk Object Type	Risk Score	Threat Objects
dest	system	50	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