Monitor Registry Keys for Print Monitors

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

The following analytic detects modifications to the registry key `HKLM\SYSTEM\CurrentControlSet\Control\Print\Monitors`. It leverages data from the Endpoint.Registry data model, focusing on events where the registry path is modified. This activity is significant because attackers can exploit this registry key to load arbitrary .dll files, which will execute with elevated SYSTEM permissions and persist after a reboot. If confirmed malicious, this could allow attackers to maintain persistence, execute code with high privileges, and potentially compromise the entire system.

name: Monitor Registry Keys for Print Monitors
id: f5f6af30-7ba7-4295-bfe9-07de87c01bbc
version: 15
creation_date: '2020-04-29'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk, Steven Dick, Bhavin Patel
status: production
type: TTP
description: The following analytic detects modifications to the registry key `HKLM\SYSTEM\CurrentControlSet\Control\Print\Monitors`. It leverages data from the Endpoint.Registry data model, focusing on events where the registry path is modified. This activity is significant because attackers can exploit this registry key to load arbitrary .dll files, which will execute with elevated SYSTEM permissions and persist after a reboot. If confirmed malicious, this could allow attackers to maintain persistence, execute code with high privileges, and potentially compromise the entire system.
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.action=modified AND Registry.registry_path="*CurrentControlSet\\Control\\Print\\Monitors*") 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)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `monitor_registry_keys_for_print_monitors_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: You will encounter noise from legitimate print-monitor registry entries.
references: []
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search  dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") | 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: New print monitor added on $dest$
    entity:
        field: dest
        type: system
        score: 50
analytic_story:
    - Suspicious Windows Registry Activities
    - Windows Persistence Techniques
    - Windows Registry Abuse
asset_type: Endpoint
mitre_attack_id:
    - T1547.010
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/attack_techniques/T1547.010/atomic_red_team/sysmon.log
          source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
          sourcetype: XmlWinEventLog
      test_type: unit

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