Detection rules › Splunk
User Discovery via Environment Variables - PowerShell (PowerShell)
Threat actors may perform user discovery to gather information about logged-in users, aiding in further lateral movement or privilege escalation within the network. This use case detects instances where PowerShell is executed with commands involving discovery of the current user's name, potentially indicating an attempt by a threat actor to discover user accounts and environment variables on a compromised system. PowerShell script block logging is recommended for best detection results. Detection using other log sources requires the PowerShell command to be run in a manner that creates a new process, such as powershell -command.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Discovery | T1033 System Owner/User Discovery |
References
Event coverage
| Provider | Event | Title |
|---|---|---|
| PowerShell | Event ID 4103 | Payload Context: ContextInfo User Data: UserData. |
| PowerShell | Event ID 4104 | Creating Scriptblock text (MessageNumber of MessageTotal). |
Rule body yaml
id: '31066.55631'
title: User Discovery via Environment Variables - PowerShell
description: Threat actors may perform user discovery to gather information about
logged-in users, aiding in further lateral movement or privilege escalation within
the network. This use case detects instances where PowerShell is executed with commands
involving discovery of the current user's name, potentially indicating an attempt
by a threat actor to discover user accounts and environment variables on a compromised
system. PowerShell script block logging is recommended for best detection results.
Detection using other log sources requires the PowerShell command to be run in a
manner that creates a new process, such as powershell -command.
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_powershell` (TERM(EventCode=4103) OR
"<EventID>4103<" OR TERM(EventCode=4104) OR "<EventID>4104<") "$env:UserName" OR
"[System.Environment]::UserName" | table _time, host, user, process, process_* |
bin span=1s | stats values(*) as * by _time, host '
techniques:
- discovery:system owner/user discovery
technique_id:
- T1033
data_category:
- PowerShell logs
references:
- https://attack.mitre.org/techniques/T1033/
- https://research.splunk.com/endpoint/0cdf318b-a0dd-47d7-b257-c621c0247de8/
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_powershell` (TERM(EventCode=4103) OR "<EventID>4103<" OR TERM(EventCode=4104) OR "<EventID>4104<") "$env:UserName" OR "[System.Environment]::UserName"
Stage 2: table
| table _time, host, user, process, process_*
Stage 3: bucket
| bin span=1s
Stage 4: stats
| stats values(*) as * by _time, host
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 |
|---|---|---|
EventCode | eq |
|
Search terms
Bare-string tokens in the SPL search body. Splunk matches each token against _raw (the untyped raw event text) anywhere it appears, not against a specific field. These don't surface in the Indicators table because they aren't predicates on a known field.
| Stage | Term |
|---|---|
| 1 | TERM |
| 1 | "<EventID>4103<" |
| 1 | TERM |
| 1 | "<EventID>4104<" |
| 1 | "$env:UserName" |
| 1 | "[System.Environment]::UserName" |