Detection: Windows Excel ActiveMicrosoftApp Child Process

Description

The following analytic identifies the execution of the ActiveMicrosoftApp process as a child of Microsoft Excel. Under normal conditions, Excel primarily spawns internal Office-related processes, and the creation of ActiveMicrosoftApp is uncommon in day-to-day business workflows. Adversaries may abuse this behavior to blend malicious activity within trusted applications, execute unauthorized code, or bypass application control mechanisms. This technique aligns with common tradecraft where Office applications are leveraged as initial access or execution vectors due to their prevalence in enterprise environments. Detecting this relationship helps defenders spot suspicious child processes that may indicate malware execution, persistence mechanisms, or attempts to establish command-and-control. Security teams should investigate the parent Excel process, the context of the ActiveMicrosoftApp execution, and any subsequent network or file activity. While certain legitimate Office features could trigger this process in specific environments, its occurrence generally warrants further scrutiny to validate intent and rule out compromise.

Search

 1
 2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
 3  WHERE Processes.parent_process_name = "EXCEL.EXE" Processes.process_name IN ("WINPROJ.EXE", "FOXPROW.exe","SCHDPLUS.exe")
 4  BY Processes.action Processes.dest Processes.original_file_name
 5     Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
 6     Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
 7     Processes.process Processes.process_exec Processes.process_guid
 8     Processes.process_hash Processes.process_id Processes.process_integrity_level
 9     Processes.process_name Processes.process_path Processes.user
10     Processes.user_id Processes.vendor_product
11
12| `drop_dm_object_name(Processes)`
13
14| `security_content_ctime(firstTime)`
15
16| `security_content_ctime(lastTime)`
17
18| `windows_excel_activemicrosoftapp_child_process_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 1	Windows	'XmlWinEventLog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'

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

Microsoft Project has been discontinued since January 2010, so its presence is unlikely in modern environments. If a related child process is observed, verify its legitimacy to rule out potential misuse.

Associated Analytic Story

• PathWiper

References

• https://specterops.io/blog/2023/10/30/lateral-movement-abuse-the-power-of-dcom-excel-application/

• https://blog.talosintelligence.com/pathwiper-targets-ukraine/

• https://www.trellix.com/blogs/research/dcom-abuse-and-network-erasure-with-trellix-ndr/

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: 3