Unusual Print Spooler Child Process

 1[metadata]
 2creation_date = "2021/07/06"
 3integration = ["endpoint", "windows", "system"]
 4maturity = "production"
 5min_stack_comments = "New fields added: required_fields, related_integrations, setup"
 6min_stack_version = "8.3.0"
 7updated_date = "2024/03/28"
 8
 9[rule]
10author = ["Elastic"]
11description = """
12Detects unusual Print Spooler service (spoolsv.exe) child processes. This may indicate an attempt to exploit privilege
13escalation vulnerabilities related to the Printing Service on Windows.
14"""
15false_positives = [
16    """
17    Install or update of a legitimate printing driver. Verify the printer driver file metadata such as manufacturer and
18    signature information.
19    """,
20]
21from = "now-9m"
22index = ["winlogbeat-*", "logs-endpoint.events.process-*", "logs-windows.*", "logs-system.security*"]
23language = "eql"
24license = "Elastic License v2"
25name = "Unusual Print Spooler Child Process"
26references = ["https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34527"]
27risk_score = 47
28rule_id = "ee5300a7-7e31-4a72-a258-250abb8b3aa1"
29setup = """## Setup
30
31If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2,
32events will not define `event.ingested` and default fallback for EQL rules was not added until version 8.2.
33Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate
34`event.ingested` to @timestamp.
35For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html
36"""
37severity = "medium"
38tags = ["Domain: Endpoint", "OS: Windows", "Use Case: Threat Detection", "Tactic: Privilege Escalation", "Use Case: Vulnerability", "Data Source: Elastic Defend"]
39timestamp_override = "event.ingested"
40type = "eql"
41
42query = '''
43process where host.os.type == "windows" and event.type == "start" and
44 process.parent.name : "spoolsv.exe" and process.command_line != null and 
45 (?process.Ext.token.integrity_level_name : "System" or ?winlog.event_data.IntegrityLevel : "System") and
46
47 /* exclusions for FP control below */
48 not process.name : ("splwow64.exe", "PDFCreator.exe", "acrodist.exe", "spoolsv.exe", "msiexec.exe", "route.exe", "WerFault.exe") and
49 not process.command_line : "*\\WINDOWS\\system32\\spool\\DRIVERS*" and
50 not (process.name : "net.exe" and process.command_line : ("*stop*", "*start*")) and
51 not (process.name : ("cmd.exe", "powershell.exe") and process.command_line : ("*.spl*", "*\\program files*", "*route add*")) and
52 not (process.name : "netsh.exe" and process.command_line : ("*add portopening*", "*rule name*")) and
53 not (process.name : "regsvr32.exe" and process.command_line : "*PrintConfig.dll*") and
54 not process.executable : (
55    "?:\\Program Files (x86)\\CutePDF Writer\\CPWriter2.exe",
56    "?:\\Program Files (x86)\\GPLGS\\gswin32c.exe"
57 )
58'''
59
60
61[[rule.threat]]
62framework = "MITRE ATT&CK"
63[[rule.threat.technique]]
64id = "T1068"
65name = "Exploitation for Privilege Escalation"
66reference = "https://attack.mitre.org/techniques/T1068/"
67
68
69[rule.threat.tactic]
70id = "TA0004"
71name = "Privilege Escalation"
72reference = "https://attack.mitre.org/tactics/TA0004/"