Detection: Windows Identify PowerShell Web Access IIS Pool

Description

This analytic detects and analyzes PowerShell Web Access (PSWA) usage in Windows environments. It tracks both connection attempts (EventID 4648) and successful logons (EventID 4624) associated with PSWA, providing a comprehensive view of access patterns. The analytic identifies PSWA's operational status, host servers, processes, and connection metrics. It highlights unique target accounts, domains accessed, and verifies logon types. This information is crucial for detecting potential misuse, such as lateral movement, brute force attempts, or unusual access patterns. By offering insights into PSWA activity, it enables security teams to quickly assess and investigate potential security incidents involving this powerful administrative tool.

Search

1`wineventlog_security` (EventCode=4648 OR EventCode=4624 OR EventCode=4625) SubjectUserName="pswa_pool" 
2| fields EventCode, SubjectUserName, TargetUserName, Computer, TargetDomainName, ProcessName, LogonType 
3| rename Computer as dest 
4| stats count(eval(EventCode=4648)) as "Connection Attempts", count(eval(EventCode=4624)) as "Successful Logons", count(eval(EventCode=4625)) as "Unsuccessful Logons", dc(TargetUserName) as "Unique Target Accounts", values(dest) as "PSWA Host", dc(TargetDomainName) as "Unique Target Domains", values(ProcessName) as "PSWA Process", values(TargetUserName) as "Target Users List", values(TargetServerName) as "Target Servers List", values(LogonType) as "Logon Types" 
5| eval PSWA_Running = "Yes", "PSWA Process" = mvindex(split(mvindex("PSWA Process", 0), "\\"), -1) 
6| fields PSWA_Running, "PSWA Host", "PSWA Process", "Connection Attempts", "Successful Logons","Unsuccessful Logons", "Unique Target Accounts", "Unique Target Domains", "Target Users List","Target Servers List", "Logon Types" 
7| `security_content_ctime(firstTime)` 
8|`security_content_ctime(lastTime)` 
9| `windows_identify_powershell_web_access_iis_pool_filter`

Data Source

Name	Platform	Sourcetype	Source
Windows Event Log Security 4648	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

To successfully implement this search, you need to be ingesting Windows Security Event logs, specifically Event ID 4648 (A logon was attempted using explicit credentials). Ensure that your Windows systems are configured to audit logon events and that these logs are being forwarded to your SIEM or log management solution. You may need to enable advanced audit policy settings in Windows to capture these events. Additionally, make sure that your environment is set up to capture the necessary fields such as SubjectUserName, TargetUserName, Computer, TargetServerName, and ProcessName from these events. If you're using Splunk, ensure that you have the appropriate Windows TA installed and configured to collect these security logs.

Known False Positives

False positives may occur if legitimate PSWA processes are used for administrative tasks. Careful review of the logs is recommended to distinguish between legitimate and malicious activity.

Associated Analytic Story

• CISA AA24-241A

Risk Based Analytics (RBA)

References

• https://www.cisa.gov/news-events/cybersecurity-advisories/aa24-241a

• https://gist.github.com/MHaggis/7e67b659af9148fa593cf2402edebb41

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: 2