Unusual Print Spooler Child Process

 1[metadata]
 2creation_date = "2021/07/06"
 3integration = ["endpoint", "windows", "system"]
 4maturity = "production"
 5updated_date = "2024/05/21"
 6
 7[rule]
 8author = ["Elastic"]
 9description = """
10Detects unusual Print Spooler service (spoolsv.exe) child processes. This may indicate an attempt to exploit privilege
11escalation vulnerabilities related to the Printing Service on Windows.
12"""
13false_positives = [
14    """
15    Install or update of a legitimate printing driver. Verify the printer driver file metadata such as manufacturer and
16    signature information.
17    """,
18]
19from = "now-9m"
20index = ["winlogbeat-*", "logs-endpoint.events.process-*", "logs-windows.*", "logs-system.security*"]
21language = "eql"
22license = "Elastic License v2"
23name = "Unusual Print Spooler Child Process"
24references = ["https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34527"]
25risk_score = 47
26rule_id = "ee5300a7-7e31-4a72-a258-250abb8b3aa1"
27setup = """## Setup
28
29If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2,
30events will not define `event.ingested` and default fallback for EQL rules was not added until version 8.2.
31Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate
32`event.ingested` to @timestamp.
33For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html
34"""
35severity = "medium"
36tags = [
37    "Domain: Endpoint",
38    "OS: Windows",
39    "Use Case: Threat Detection",
40    "Tactic: Privilege Escalation",
41    "Use Case: Vulnerability",
42    "Data Source: Elastic Defend",
43]
44timestamp_override = "event.ingested"
45type = "eql"
46
47query = '''
48process where host.os.type == "windows" and event.type == "start" and
49 process.parent.name : "spoolsv.exe" and process.command_line != null and 
50 (?process.Ext.token.integrity_level_name : "System" or ?winlog.event_data.IntegrityLevel : "System") and
51
52 /* exclusions for FP control below */
53 not process.name : ("splwow64.exe", "PDFCreator.exe", "acrodist.exe", "spoolsv.exe", "msiexec.exe", "route.exe", "WerFault.exe") and
54 not process.command_line : "*\\WINDOWS\\system32\\spool\\DRIVERS*" and
55 not (process.name : "net.exe" and process.command_line : ("*stop*", "*start*")) and
56 not (process.name : ("cmd.exe", "powershell.exe") and process.command_line : ("*.spl*", "*\\program files*", "*route add*")) and
57 not (process.name : "netsh.exe" and process.command_line : ("*add portopening*", "*rule name*")) and
58 not (process.name : "regsvr32.exe" and process.command_line : "*PrintConfig.dll*") and
59 not process.executable : (
60    "?:\\Program Files (x86)\\CutePDF Writer\\CPWriter2.exe",
61    "?:\\Program Files (x86)\\GPLGS\\gswin32c.exe"
62 )
63'''
64
65
66[[rule.threat]]
67framework = "MITRE ATT&CK"
68[[rule.threat.technique]]
69id = "T1068"
70name = "Exploitation for Privilege Escalation"
71reference = "https://attack.mitre.org/techniques/T1068/"
72
73
74[rule.threat.tactic]
75id = "TA0004"
76name = "Privilege Escalation"
77reference = "https://attack.mitre.org/tactics/TA0004/"