Enable RDP In Other Port Number

SPLUNK detection rule by Teoderick Contreras, Splunk, Steven Dick · Apache-2.0

The following analytic detects modifications to the registry that enable RDP on a machine using a non-default port number. It leverages data from the Endpoint.Registry data model, specifically monitoring changes to the registry path "HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp" and the "PortNumber" value. This activity is significant as attackers often modify RDP settings to facilitate lateral movement and maintain remote access to compromised systems. If confirmed malicious, this could allow attackers to bypass network defenses, gain persistent access, and potentially control the compromised machine.

name: Enable RDP In Other Port Number
id: 99495452-b899-11eb-96dc-acde48001122
version: 18
creation_date: '2021-05-19'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk, Steven Dick
status: production
type: TTP
description: The following analytic detects modifications to the registry that enable RDP on a machine using a non-default port number. It leverages data from the Endpoint.Registry data model, specifically monitoring changes to the registry path "HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp" and the "PortNumber" value. This activity is significant as attackers often modify RDP settings to facilitate lateral movement and maintain remote access to compromised systems. If confirmed malicious, this could allow attackers to bypass network defenses, gain persistent access, and potentially control the compromised machine.
data_source:
    - Sysmon EventID 13
search: '| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Registry WHERE (Registry.registry_path="*\\CurrentControlSet\\Control\\Terminal Server\\WinStations\\RDP-Tcp*" Registry.registry_value_name = "PortNumber") by Registry.action Registry.dest Registry.process_guid Registry.process_id Registry.registry_hive Registry.registry_path Registry.registry_key_name Registry.registry_value_data Registry.registry_value_name Registry.registry_value_type Registry.status Registry.user Registry.vendor_product | `drop_dm_object_name(Registry)` | where isnotnull(registry_value_data) | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `enable_rdp_in_other_port_number_filter`'
how_to_implement: To successfully implement this search, you need to be ingesting logs with the registry value name, registry path, and registry value data from your endpoints. If you are using Sysmon, you must have at least version 2.0 of the official Sysmon TA. https://splunkbase.splunk.com/app/5709
known_false_positives: No false positives have been identified at this time.
references:
    - https://www.mvps.net/docs/how-to-secure-remote-desktop-rdp/
drilldown_searches:
    - name: View the detection results for - "$user$" and "$dest$"
      search: '%original_detection_search% | search  user = "$user$" dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$" and "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$", "$dest$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
finding:
    title: RDP was moved to a non-standard port on $dest$ by $user$.
    entity:
        field: user
        type: user
        score: 50
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 50
          message: RDP was moved to a non-standard port on $dest$ by $user$.
analytic_story:
    - Prohibited Traffic Allowed or Protocol Mismatch
    - Windows Registry Abuse
    - Windows RDP Artifacts and Defense Evasion
    - Interlock Ransomware
asset_type: Endpoint
mitre_attack_id:
    - T1021
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/honeypots/casper/datasets1/windows-sysmon.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit

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29f51065-200f-4b23-81c0-9cb05599ebed

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