Detection: Windows SharePoint Spinstall0 Webshell File Creation

Updated Date: 2025-07-21 ID: 7a0dda67-4cc7-4113-b3bd-b3f1489a98bf Author: Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

This detection identifies the creation or modification of the "spinstall0.aspx" webshell file in Microsoft SharePoint directories. This file is a known indicator of compromise associated with the exploitation of CVE-2025-53770 (ToolShell vulnerability). Attackers exploit the vulnerability to drop webshells that provide persistent access to compromised SharePoint servers, allowing them to execute arbitrary commands, access sensitive data, and move laterally within the network.

Search

1
2| tstats count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Filesystem where Filesystem.file_name="spinstall0.aspx" AND (Filesystem.file_path="*\\microsoft shared\\Web Server Extensions\\16\\TEMPLATE\\LAYOUTS*" OR Filesystem.file_path="*\\microsoft shared\\Web Server Extensions\\15\\TEMPLATE\\LAYOUTS*") by Filesystem.dest Filesystem.user Filesystem.file_create_time Filesystem.file_name Filesystem.file_path Filesystem.action Filesystem.process_guid Filesystem.process_id Filesystem.vendor_product 
3| `drop_dm_object_name(Filesystem)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `windows_sharepoint_spinstall0_webshell_file_creation_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 11	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
windows_sharepoint_spinstall0_webshell_file_creation_filter	`search *`

windows_sharepoint_spinstall0_webshell_file_creation_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1190	Exploit Public-Facing Application	Initial Access
T1505.003	Web Shell	Persistence

Delivery

Installation

DE.CM

CIS 10

Default Configuration

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

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

To successfully implement this search, you need to be ingesting logs with the file name, file path, and process information from your endpoints. If you are using Sysmon, you must have at least Sysmon version 6.0.4 with Event Code 11 enabled. You can also use other EDR products or Windows Event Logs that capture file creation events. The detection requires the Endpoint data model, populated with file creation events in the SharePoint directories.

Known False Positives

Limited false positives are expected as the spinstall0.aspx file is not a legitimate SharePoint component. However, there might be rare cases where legitimate files with similar names are created during SharePoint updates or maintenance. Verify the process that created the file and the file content to confirm malicious intent.

Associated Analytic Story

Microsoft SharePoint Vulnerabilities

Risk Based Analytics (RBA)

Risk Message:

Potential SharePoint webshell (spinstall0.aspx) detected on $dest$ related to CVE-2025-53770.

Risk Object	Risk Object Type	Risk Score	Threat Objects
dest	system	90	file_name

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`

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: 1