Detection rules › Splunk
Print Spooler Adding A Printer Driver
The following analytic detects the addition of new printer drivers by monitoring Windows PrintService operational logs, specifically EventCode 316. This detection leverages log data to identify messages indicating the addition or update of printer drivers, such as "kernelbase.dll" and "UNIDRV.DLL." This activity is significant as it may indicate exploitation attempts related to vulnerabilities like CVE-2021-34527 (PrintNightmare). If confirmed malicious, attackers could gain code execution or escalate privileges, potentially compromising the affected system. Immediate isolation and investigation of the endpoint are recommended.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Persistence | T1547.012 Boot or Logon Autostart Execution: Print Processors |
| Privilege Escalation | T1547.012 Boot or Logon Autostart Execution: Print Processors |
Event coverage
| Provider | Event | Title |
|---|---|---|
| PrintService | Event ID 316 | Printer driver param1 for param2 param3 was added or updated. |
Rule body splunk
name: Print Spooler Adding A Printer Driver
id: 313681a2-da8e-11eb-adad-acde48001122
version: 12
creation_date: '2021-07-01'
modification_date: '2026-05-13'
author: Mauricio Velazco, Michael Haag, Teoderick Contreras, Splunk
status: production
type: TTP
description: The following analytic detects the addition of new printer drivers by monitoring Windows PrintService operational logs, specifically EventCode 316. This detection leverages log data to identify messages indicating the addition or update of printer drivers, such as "kernelbase.dll" and "UNIDRV.DLL." This activity is significant as it may indicate exploitation attempts related to vulnerabilities like CVE-2021-34527 (PrintNightmare). If confirmed malicious, attackers could gain code execution or escalate privileges, potentially compromising the affected system. Immediate isolation and investigation of the endpoint are recommended.
data_source:
- Windows Event Log Printservice 316
search: |-
`printservice` EventCode=316 category = "Adding a printer driver" Message = "*kernelbase.dll,*" Message = "*UNIDRV.DLL,*" Message = "*.DLL.*"
| stats count min(_time) as firstTime max(_time) as lastTime
BY OpCode EventCode ComputerName
Message
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `print_spooler_adding_a_printer_driver_filter`
how_to_implement: You will need to ensure PrintService Admin and Operational logs are being logged to Splunk from critical or all systems.
known_false_positives: No false positives have been identified at this time.
references:
- https://twitter.com/MalwareJake/status/1410421445608476679?s=20
- https://www.truesec.com/hub/blog/fix-for-printnightmare-cve-2021-1675-exploit-to-keep-your-print-servers-running-while-a-patch-is-not-available
- https://www.truesec.com/hub/blog/exploitable-critical-rce-vulnerability-allows-regular-users-to-fully-compromise-active-directory-printnightmare-cve-2021-1675
- https://www.reddit.com/r/msp/comments/ob6y02/critical_vulnerability_printnightmare_exposes
drilldown_searches:
- name: View the detection results for - "$ComputerName$"
search: '%original_detection_search% | search ComputerName = "$ComputerName$"'
earliest_offset: $info_min_time$
latest_offset: $info_max_time$
- name: View risk events for the last 7 days for - "$ComputerName$"
search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$ComputerName$") | 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: Suspicious print driver was loaded on endpoint $ComputerName$.
entity:
field: ComputerName
type: system
score: 50
analytic_story:
- PrintNightmare CVE-2021-34527
- Black Basta Ransomware
asset_type: Endpoint
cve:
- CVE-2021-34527
- CVE-2021-1675
mitre_attack_id:
- T1547.012
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/T1547.012/printnightmare/windows-printservice_operational.log
source: WinEventLog:Microsoft-Windows-PrintService/Operational
sourcetype: WinEventLog
test_type: unit
Stages and Predicates
Stage 1: search
`printservice` EventCode=316 category = "Adding a printer driver" Message = "*kernelbase.dll,*" Message = "*UNIDRV.DLL,*" Message = "*.DLL.*"
Stage 2: stats
| stats count min(_time) as firstTime max(_time) as lastTime
BY OpCode EventCode ComputerName
Message
Stage 3: search
| `security_content_ctime(firstTime)`
Stage 4: search
| `security_content_ctime(lastTime)`
Stage 5: search
| `print_spooler_adding_a_printer_driver_filter`
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.