The following analytic utilizes PowerShell Script Block Logging (EventCode=4104) to identify suspicious PowerShell execution. Script Block Logging captures the command sent to PowerShell, the full command to be executed. Upon enabling, logs will output to Windows event logs. Dependent upon volume, enable on critical endpoints or all.
This analytic identifies Get-ForestTrust from PowerSploit in order to gather domain trust information.
During triage, review parallel processes using an EDR product or 4688 events. It will be important to understand the timeline of events around this activity. Review the entire logged PowerShell script block.
- Type: TTP
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2022-02-24
- Author: Michael Haag, Splunk
- ID: 70fac80e-0bf1-11ec-9ba0-acde48001122
Kill Chain Phase
- CIS 10
1 2 3 4 5 6 7 `powershell` EventCode=4104 ScriptBlockText = "*get-foresttrust*" | stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText Computer UserID | rename Computer as dest | rename UserID as user | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `get_foresttrust_with_powershell_script_block_filter`
The SPL above uses the following Macros:
get-foresttrust_with_powershell_script_block_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
How To Implement
To successfully implement this analytic, you will need to enable PowerShell Script Block Logging on some or all endpoints. Additional setup here https://docs.splunk.com/Documentation/UBA/22.214.171.124/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell.
Known False Positives
False positives may be present. Tune as needed.
Associated Analytic Story
|12.0||30||40||Suspicious PowerShell Get-ForestTrust was identified on endpoint $dest$ by user $user$.|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
source | version: 2