splunk_escuHunting

Windows Identify Protocol Handlers

The following analytic identifies the use of protocol handlers executed via the command line. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process and command-line telemetry. This activity is significant because protocol handlers can be exploited to execute arbitrary commands or launch applications, potentially leading to unauthorized actions. If confirmed malicious, an attacker could use this technique to gain code execution, escalate privileges, or maintain persistence within the environment, posing a significant security risk.

MITRE ATT&CK

T1059

execution

Detection Query

| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime values(Processes.process) as process values(Processes.parent_process) as parent_process FROM datamodel=Endpoint.Processes
  BY Processes.action Processes.dest Processes.original_file_name
     Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
     Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
     Processes.process Processes.process_exec Processes.process_guid
     Processes.process_hash Processes.process_id Processes.process_integrity_level
     Processes.process_name Processes.process_path Processes.user
     Processes.user_id Processes.vendor_product
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `drop_dm_object_name(Processes)`
| lookup windows_protocol_handlers handler AS process OUTPUT handler ishandler
| where ishandler="TRUE"
| `windows_identify_protocol_handlers_filter`

Author

Michael Haag, Splunk

Created

2026-02-25

Data Sources

Sysmon EventID 1Windows Event Log Security 4688CrowdStrike ProcessRollup2

References

Tags

Living Off The Land

Raw Content

name: Windows Identify Protocol Handlers
id: bd5c311e-a6ea-48ae-a289-19a3398e3648
version: 9
date: '2026-02-25'
author: Michael Haag, Splunk
status: production
type: Hunting
description: The following analytic identifies the use of protocol handlers executed via the command line. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process and command-line telemetry. This activity is significant because protocol handlers can be exploited to execute arbitrary commands or launch applications, potentially leading to unauthorized actions. If confirmed malicious, an attacker could use this technique to gain code execution, escalate privileges, or maintain persistence within the environment, posing a significant security risk.
data_source:
    - Sysmon EventID 1
    - Windows Event Log Security 4688
    - CrowdStrike ProcessRollup2
search: |-
    | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime values(Processes.process) as process values(Processes.parent_process) as parent_process FROM datamodel=Endpoint.Processes
      BY Processes.action Processes.dest Processes.original_file_name
         Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
         Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
         Processes.process Processes.process_exec Processes.process_guid
         Processes.process_hash Processes.process_id Processes.process_integrity_level
         Processes.process_name Processes.process_path Processes.user
         Processes.user_id Processes.vendor_product
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `drop_dm_object_name(Processes)`
    | lookup windows_protocol_handlers handler AS process OUTPUT handler ishandler
    | where ishandler="TRUE"
    | `windows_identify_protocol_handlers_filter`
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: False positives will be found. https and http is a URL Protocol handler that will trigger this analytic. Tune based on process or command-line.
references:
    - https://gist.github.com/MHaggis/a0d3edb57d36e0916c94c0a464b2722e
    - https://www.oreilly.com/library/view/learning-java/1565927184/apas02.html
    - https://blogs.windows.com/msedgedev/2022/01/20/getting-started-url-protocol-handlers-microsoft-edge/
    - https://github.com/Mr-Un1k0d3r/PoisonHandler
    - https://www.mdsec.co.uk/2021/03/phishing-users-to-take-a-test/
    - https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218/T1218.md#atomic-test-5---protocolhandlerexe-downloaded-a-suspicious-file
    - https://techcommunity.microsoft.com/t5/windows-it-pro-blog/disabling-the-msix-ms-appinstaller-protocol-handler/ba-p/3119479
    - https://www.huntress.com/blog/microsoft-office-remote-code-execution-follina-msdt-bug
    - https://parsiya.net/blog/2021-03-17-attack-surface-analysis-part-2-custom-protocol-handlers/
tags:
    analytic_story:
        - Living Off The Land
    asset_type: Endpoint
    mitre_attack_id:
        - T1059
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1059/protocol_handlers/protocolhandlers.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog