Windows IIS Components New Module Added

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Description

The following analytic uses the Windows Event log - Microsoft-IIS-Configuration/Operational - which must be enabled and logged on Windows IIS servers before it can be Splunked. The following analytic identifies newly installed IIS modules. Per Microsoft, IIS modules are not commonly added to a production IIS server, so alerting on this event ID should be enabled.IIS modules can be installed at a global level or at a site level. In detecting malicious IIS modules, it is important to check both the global and site level for unauthorized modules. Regular monitoring of these locations for such modules and comparing against a known good list can help detect and identify malicious IIS modules.

• Type: TTP

• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

• Last Updated: 2022-12-19
• Author: Michael Haag, Splunk
• ID: 55f22929-cfd3-4388-ba5c-4d01fac7ee7e

Annotations

ATT&CK

ATT&CK

ID	Technique	Tactic
T1505	Server Software Component	Persistence

T1505.004

IIS Components

Persistence

Kill Chain Phase

• Installation

NIST

• DE.CM

CIS20

• CIS 10

CVE

Search

`iis_operational_logs` EventCode=29 
| stats  count min(_time) as firstTime max(_time) as lastTime by OpCode EventCode ComputerName Message 
| rename ComputerName AS dest 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `windows_iis_components_new_module_added_filter`

Macros

The SPL above uses the following Macros:

• iis_operational_logs
• security_content_ctime

windows_iis_components_new_module_added_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
• OpCode
• EventCode
• ComputerName
• Message

How To Implement

You must enabled the IIS Configuration Operational log before ingesting in Splunk. Setup and inputs may be found here https://gist.github.com/MHaggis/64396dfd9fc3734e1d1901a8f2f07040.

Known False Positives

False positives may be present when updates or an administrator adds a new module to IIS. Monitor and filter as needed.

Associated Analytic Story

• IIS Components

RBA

Risk Score	Impact	Confidence	Message
48.0	60	80	A new IIS Module has been loaded and should be reviewed on $dest$.

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

• https://gist.github.com/MHaggis/64396dfd9fc3734e1d1901a8f2f07040
• 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

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

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