Detection: Windows IIS Components Add New Module

Description

The following analytic detects the execution of AppCmd.exe to install a new module in IIS. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and command-line executions. This activity is significant as adversaries may use it to install webshells or backdoors, leading to credit card scraping, persistence, and further post-exploitation. If confirmed malicious, this could allow attackers to maintain persistent access, execute arbitrary code, and potentially exfiltrate sensitive information from the compromised web server.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where NOT (Processes.parent_process_name  IN ("msiexec.exe", "iissetup.exe")) Processes.process_name=appcmd.exe Processes.process IN ("*install *", "*module *") AND Processes.process="*image*" by Processes.dest Processes.user Processes.parent_process_name 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| `windows_iis_components_add_new_module_filter`

Data Source

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

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 may be present until properly tuned. Filter as needed.

Associated Analytic Story

• IIS Components

Risk Based Analytics (RBA)

References

• https://www.microsoft.com/en-us/security/blog/2022/12/12/iis-modules-the-evolution-of-web-shells-and-how-to-detect-them/

• https://www.crowdstrike.com/wp-content/uploads/2022/05/crowdstrike-iceapple-a-novel-internet-information-services-post-exploitation-framework-1.pdf

• https://unit42.paloaltonetworks.com/unit42-oilrig-uses-rgdoor-iis-backdoor-targets-middle-east/

• https://www.secureworks.com/research/bronze-union

• https://github.com/redcanaryco/atomic-red-team/tree/master/atomics/T1505.004

• https://strontic.github.io/xcyclopedia/library/appcmd.exe-055B2B09409F980BF9B5A3969D01E5B2.html

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: 4