Detection rules › Splunk
Print Spooler Failed to Load a Plug-in
The following analytic detects driver load errors in the Windows PrintService Admin logs, specifically identifying issues related to CVE-2021-34527 (PrintNightmare). It triggers on error messages indicating the print spooler failed to load a plug-in module, such as "meterpreter.dll," with error code 0x45A. This detection method leverages specific event codes and error messages. This activity is significant as it may indicate an exploitation attempt of a known vulnerability. If confirmed malicious, an attacker could gain unauthorized code execution on the affected system, leading to potential system compromise.
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 808 | The print spooler failed to load a plug-in module PluginDllName, error code ErrorCode. |
| PrintService | Event ID 4909 | Print Service event 4909 (manifest stub). |
Rule body splunk
name: Print Spooler Failed to Load a Plug-in
id: 1adc9548-da7c-11eb-8f13-acde48001122
version: 10
creation_date: '2021-07-01'
modification_date: '2026-05-13'
author: Mauricio Velazco, Michael Haag, Splunk
status: production
type: TTP
description: The following analytic detects driver load errors in the Windows PrintService Admin logs, specifically identifying issues related to CVE-2021-34527 (PrintNightmare). It triggers on error messages indicating the print spooler failed to load a plug-in module, such as "meterpreter.dll," with error code 0x45A. This detection method leverages specific event codes and error messages. This activity is significant as it may indicate an exploitation attempt of a known vulnerability. If confirmed malicious, an attacker could gain unauthorized code execution on the affected system, leading to potential system compromise.
data_source:
- Windows Event Log Printservice 808
- Windows Event Log Printservice 4909
search: '`printservice` ((ErrorCode="0x45A" (EventCode="808" OR EventCode="4909")) OR ("The print spooler failed to load a plug-in module" OR "\\drivers\\x64\\")) | 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_failed_to_load_a_plug_in_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: False positives are unknown and filtering may be required.
references:
- 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 printer spooler errors have occurred on endpoint $ComputerName$ with EventCode $EventCode$.
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_admin.log
source: WinEventLog:Microsoft-Windows-PrintService/Admin
sourcetype: WinEventLog
test_type: unit
Stages and Predicates
Stage 1: search
`printservice` ((ErrorCode="0x45A" (EventCode="808" OR EventCode="4909")) OR ("The print spooler failed to load a plug-in module" OR "\\drivers\\x64\\"))
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_failed_to_load_a_plug_in_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.
Search terms
Bare-string tokens in the SPL search body. Splunk matches each token against _raw (the untyped raw event text) anywhere it appears, not against a specific field. These don't surface in the Indicators table because they aren't predicates on a known field.
| Stage | Term |
|---|---|
| 1 | "The print spooler failed to load a plug-in module" |
| 1 | "\\drivers\\x64\\" |