Detection: Windows IIS Components New Module Added

Updated Date: 2024-09-30 ID: 55f22929-cfd3-4388-ba5c-4d01fac7ee7e Author: Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the addition of new IIS modules on a Windows IIS server. It leverages the Windows Event log - Microsoft-IIS-Configuration/Operational, specifically EventCode 29, to identify this activity. This behavior is significant because IIS modules are rarely added to production servers, and unauthorized modules could indicate malicious activity. If confirmed malicious, an attacker could use these modules to execute arbitrary code, escalate privileges, or maintain persistence within the environment, potentially compromising the server and sensitive data.

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

Data Source

Name Platform Sourcetype Source
Windows IIS 29 Windows icon Windows 'IIS:Configuration:Operational' 'IIS:Configuration:Operational'

Macros Used

Name Value
iis_operational_logs sourcetype="IIS:Configuration:Operational"
windows_iis_components_new_module_added_filter search *
windows_iis_components_new_module_added_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
T1505 Server Software Component Persistence
T1505.004 IIS Components Persistence
KillChainPhase.INSTALLATION
NistCategory.DE_CM
Cis18Value.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

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

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
A new IIS Module has been loaded and should be reviewed on $dest$. 48 60 80
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset IIS:Configuration:Operational IIS:Configuration:Operational
Integration ✅ Passing Dataset IIS:Configuration:Operational IIS:Configuration:Operational

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: 3