Windows XLL File Creation Outside of Typical Location
Description
Detects the creation of an XLL file outside of typical locations. This can indicate an attempt to abuse Excel COM objects to load and execute a malicious XLL.
Query · spl
| tstats `security_content_summariesonly`
count min(_time) as firstTime
max(_time) as lastTime
from datamodel=Endpoint.Filesystem where
Filesystem.file_path="*.xll"
NOT Filesystem.file_path IN (
"*:\\Program Files\\Microsoft Office\\*",
"*\\AppData\\Roaming\\Microsoft\\AddIns\\*"
)
by Filesystem.dest Filesystem.file_create_time Filesystem.process_path
Filesystem.process_guid Filesystem.process_id Filesystem.file_path
Filesystem.action Filesystem.file_name
Filesystem.user Filesystem.vendor_product
| `drop_dm_object_name(Filesystem)`
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `windows_xll_file_creation_outside_of_typical_location_filter`
Implementation guide
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
- Some legitimate Excel add-ins and administrative tools may create XLL files outside typical locations. Review and allow approved applications to reduce false positives.
Analyst notes
Known false positives: Some legitimate Excel add-ins and administrative tools may create XLL files outside typical locations. Review and allow approved applications to reduce false positives.