Detection: Winword Spawning PowerShell

Description

The following analytic has been deprecated in favour of a more generic approach in "Windows Office Product Spawned Uncommon Process". The following analytic identifies instances where Microsoft Word (winword.exe) spawns a PowerShell process. This behavior is detected using Endpoint Detection and Response (EDR) telemetry, focusing on process creation events where the parent process is winword.exe. This activity is significant because it is uncommon and often associated with spearphishing attacks, where malicious documents execute encoded PowerShell commands. If confirmed malicious, this could allow an attacker to execute arbitrary code, potentially leading to data exfiltration, system compromise, or further lateral movement within the network.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.parent_process_name="winword.exe" `process_powershell` by Processes.dest Processes.user Processes.parent_process_name Processes.parent_process Processes.process_name Processes.original_file_name Processes.process Processes.process_id Processes.parent_process_id 
3| `drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)`
5| `security_content_ctime(lastTime)` 
6| `winword_spawning_powershell_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 1	Windows	'XmlWinEventLog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Windows Event Log Security 4688	Windows	'XmlWinEventLog'	'XmlWinEventLog:Security'
CrowdStrike ProcessRollup2	Other	'crowdstrike:events:sensor'	'crowdstrike'

Macros Used

Annotations

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

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

Associated Analytic Story

• Spearphishing Attachments

• Compromised Windows Host

• CVE-2023-21716 Word RTF Heap Corruption

• DarkCrystal RAT

References

• https://redcanary.com/threat-detection-report/techniques/powershell/

• https://attack.mitre.org/techniques/T1566/001/

• https://app.any.run/tasks/b79fa381-f35c-4b3e-8d02-507e7ee7342f/

• https://app.any.run/tasks/181ac90b-0898-4631-8701-b778a30610ad/

Detection Testing

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: 8