splunk-security_content/docs/_posts/2021-04-12-excel_spawning_powershell.md

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title	excerpt	categories	last_modified_at	toc	toc_label	tags
Excel Spawning PowerShell	Security Account Manager , OS Credential Dumping	Endpoint	2021-04-12	true		Security Account Manager OS Credential Dumping Credential Access Credential Access Splunk Enterprise Splunk Enterprise Security Splunk Cloud Endpoint

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Description

The following detection identifies Microsoft Excel spawning PowerShell. Typically, this is not common behavior and not default with Excel.exe. Excel.exe will generally be found in the following path C:\Program Files\Microsoft Office\root\Office16 (version will vary). PowerShell spawning from Excel.exe is common for a spearphishing attachment and is actively used. Albeit, the command executed will most likely be encoded and captured via another detection. During triage, review parallel processes and identify any files that may have been written.

• Type: TTP
• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
• Datamodel: Endpoint- Datasource: Splunk Add-on for Sysmon
• Last Updated: 2021-04-12
• Author: Michael Haag, Splunk
• ID: 42d40a22-9be3-11eb-8f08-acde48001122

Annotations

ATT&CK

ID	Technique	Tactic
T1003.002	Security Account Manager	Credential Access

| T1003 | OS Credential Dumping | Credential Access |

Kill Chain Phase

• Exploitation

NIST

CIS20

CVE

Search

| tstats `security_content_summariesonly` count values(Processes.process) min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.parent_process_name="excel.exe" `process_powershell` by Processes.parent_process Processes.process_name Processes.user Processes.dest Processes.original_file_name 
| `drop_dm_object_name("Processes")` 
| `security_content_ctime(firstTime)`
|`security_content_ctime(lastTime)` 
| `excel_spawning_powershell_filter`

Macros

The SPL above uses the following Macros:

• security_content_ctime
• security_content_summariesonly
• process_powershell

ℹ️ excel_spawning_powershell_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required field

• Processes.dest
• Processes.user
• Processes.parent_process_name
• Processes.parent_process
• Processes.original_file_name
• Processes.process_name
• Processes.process
• Processes.process_id
• Processes.parent_process_path
• Processes.process_path
• Processes.parent_process_id

How To Implement

To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint datamodel in the Processes node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.

Known False Positives

False positives should be limited, but if any are present, filter as needed.

Associated Analytic story

• Spearphishing Attachments

RBA

Risk Score	Impact	Confidence	Message
80.0	80	100	An instance of parent_process_name spawning process_name was identified on endpoint dest by user user, indicating potential suspicious macro execution.

ℹ️ The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

• https://redcanary.com/threat-detection-report/techniques/powershell/
• https://attack.mitre.org/techniques/T1566/001/

Test Dataset

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

• https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1566.001/macro/windows-sysmon.log

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