ESXi Reverse Shell Patterns

SPLUNK detection rule by Raven Tait, Splunk · Apache-2.0

This detection looks for reverse shell string patterns on an ESXi host, which may indicate that a threat actor is attempting to establish remote control over the system.

name: ESXi Reverse Shell Patterns
id: ee8b16a4-118e-4dd7-af4b-835530415610
version: 4
creation_date: '2025-07-11'
modification_date: '2026-05-13'
author: Raven Tait, Splunk
status: production
type: TTP
description: This detection looks for reverse shell string patterns on an ESXi host, which may indicate that a threat actor is attempting to establish remote control over the system.
data_source:
    - VMWare ESXi Syslog
search: '`esxi_syslog` Message IN ("*bash -i >&*","*/dev/tcp/*","*/dev/udp/*", "*/socat exec:*","*socket(S,PF_INET*") OR (Message="*python -c*" AND Message="*import socket*") | 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_reverse_shell_patterns_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: Reverse shell patterns seen 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:
    - T1059
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/T1059/esxi_reverse_shell/esxi_reverse_shell.log
          source: vmware:esxlog
          sourcetype: vmw-syslog
      test_type: unit

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

55e7f8df-8413-4cd0-b2b5-0592ab24b031

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Executable code, not a declarative rule

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Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

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