W3WP Spawning Shell
Description
The following analytic identifies instances where a shell (PowerShell.exe or Cmd.exe) is spawned from W3WP.exe, the IIS worker process. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process creation events where the parent process is W3WP.exe. This activity is significant as it may indicate webshell activity, often associated with exploitation attempts like those by the HAFNIUM Group on Exchange servers. If confirmed malicious, this behavior could allow attackers to execute arbitrary commands, potentially leading to system compromise, data exfiltration, or further lateral movement within the network.
- Type: TTP
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Endpoint
- Last Updated: 2024-05-16
- Author: Michael Haag, Splunk
- ID: 0f03423c-7c6a-11eb-bc47-acde48001122
Annotations
ATT&CK
Kill Chain Phase
- Installation
NIST
- DE.CM
CIS20
- CIS 10
CVE
Search
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| tstats `security_content_summariesonly` count values(Processes.process_name) as process_name values(Processes.process) as process min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.parent_process_name=w3wp.exe AND `process_cmd` OR `process_powershell` by Processes.dest Processes.parent_process Processes.original_file_name Processes.user
| `drop_dm_object_name(Processes)`
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `w3wp_spawning_shell_filter`
Macros
The SPL above uses the following Macros:
w3wp_spawning_shell_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Required fields
List of fields required to use this analytic.
- _time
- 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
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
Baseline your environment before production. It is possible build systems using IIS will spawn cmd.exe to perform a software build. Filter as needed.
Associated Analytic Story
- ProxyNotShell
- Data Destruction
- ProxyShell
- Hermetic Wiper
- CISA AA22-257A
- HAFNIUM Group
- BlackByte Ransomware
- CISA AA22-264A
- Flax Typhoon
- WS FTP Server Critical Vulnerabilities
RBA
| Risk Score | Impact | Confidence | Message |
|---|---|---|---|
| 56.0 | 70 | 80 | Possible Web Shell execution on $dest$ |
Reference
- https://www.microsoft.com/security/blog/2020/02/04/ghost-in-the-shell-investigating-web-shell-attacks/
- https://www.zerodayinitiative.com/blog/2021/8/17/from-pwn2own-2021-a-new-attack-surface-on-microsoft-exchange-proxyshell
- https://www.youtube.com/watch?v=FC6iHw258RI
- https://www.huntress.com/blog/rapid-response-microsoft-exchange-servers-still-vulnerable-to-proxyshell-exploit#what-should-you-do
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
source | version: 3