GitHub Repo

Detection: Windows Default Cobalt Strike PowerShell Beacon

Updated Date: 2026-04-13 ID: 25b6329b-d6b7-4ccd-9ac2-6ca1dfd2b0c1 Author: Raven Tait, Splunk Type: TTP Product: Splunk Enterprise Security

Description

Detects default function and variable names known to be used by the Cobalt Strike PowerShell beacon. This beacon is used to gain command and control on a victim.

 1`powershell`
 2EventID="4104"
 3ScriptBlockText IN (
 4    "*func_get_proc_address*",
 5    "*$var_unsafe_native_methods*",
 6    "*$var_gpa.Invoke*",
 7    "*func_get_delegate_type*",
 8    "*$var_type_builder*"
 9)
10
11| fillnull
12
13| stats count min(_time) as firstTime
14              max(_time) as lastTime
15
16by Computer EventID ScriptBlockText dest signature signature_id
17   user_id vendor_product Guid Opcode Name
18   Path ProcessID ScriptBlockId
19
20
21| `security_content_ctime(firstTime)`
22
23| `security_content_ctime(lastTime)`
24
25| `windows_default_cobalt_strike_powershell_beacon_filter`

Data Source

Name Platform Sourcetype Source
Powershell Script Block Logging 4104 Windows icon Windows 'XmlWinEventLog' 'XmlWinEventLog:Microsoft-Windows-PowerShell/Operational'

Macros Used

Name Value
powershell (source=WinEventLog:Microsoft-Windows-PowerShell/Operational OR source="XmlWinEventLog:Microsoft-Windows-PowerShell/Operational" OR source=WinEventLog:PowerShellCore/Operational OR source="XmlWinEventLog:PowerShellCore/Operational")
windows_default_cobalt_strike_powershell_beacon_filter search *
windows_default_cobalt_strike_powershell_beacon_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
T1059.001 PowerShell Execution
T1204.002 Malicious File Execution
Installation
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

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

Known False Positives

False positives are very unlikely as this detection targets default Cobalt Strike PowerShell beacon functions and variables. Modifications to the beacon's script may bypass detection but do not create false positives.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

Default Cobalt Strike PowerShell beacon activity observed on $dest$ via script block $ScriptBlockId$.

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 XmlWinEventLog:Microsoft-Windows-PowerShell/Operational XmlWinEventLog
Integration ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-PowerShell/Operational XmlWinEventLog

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