Suspicious Explorer Child Process

  1[metadata]
  2creation_date = "2020/10/29"
  3integration = ["endpoint", "windows"]
  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 = """
 12Identifies a suspicious Windows explorer child process. Explorer.exe can be abused to launch malicious scripts or
 13executables from a trusted parent process.
 14"""
 15from = "now-9m"
 16index = ["logs-endpoint.events.process-*", "winlogbeat-*", "logs-windows.sysmon_operational-*", "endgame-*"]
 17language = "eql"
 18license = "Elastic License v2"
 19name = "Suspicious Explorer Child Process"
 20risk_score = 47
 21rule_id = "9a5b4e31-6cde-4295-9ff7-6be1b8567e1b"
 22setup = """## Setup
 23
 24If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2,
 25events will not define `event.ingested` and default fallback for EQL rules was not added until version 8.2.
 26Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate
 27`event.ingested` to @timestamp.
 28For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html
 29"""
 30severity = "medium"
 31tags = ["Domain: Endpoint", "OS: Windows", "Use Case: Threat Detection", "Tactic: Initial Access", "Tactic: Defense Evasion", "Tactic: Execution", "Data Source: Elastic Endgame", "Data Source: Elastic Defend", "Data Source: Sysmon"]
 32timestamp_override = "event.ingested"
 33type = "eql"
 34
 35query = '''
 36process where host.os.type == "windows" and event.type == "start" and
 37  (
 38   process.name : ("cscript.exe", "wscript.exe", "powershell.exe", "rundll32.exe", "cmd.exe", "mshta.exe", "regsvr32.exe") or
 39   process.pe.original_file_name in ("cscript.exe", "wscript.exe", "PowerShell.EXE", "RUNDLL32.EXE", "Cmd.Exe", "MSHTA.EXE", "REGSVR32.EXE")
 40  ) and
 41  /* Explorer started via DCOM */
 42  process.parent.name : "explorer.exe" and process.parent.args : "-Embedding" and
 43  not process.parent.args:
 44          (
 45            /* Noisy CLSID_SeparateSingleProcessExplorerHost Explorer COM Class IDs   */
 46            "/factory,{5BD95610-9434-43C2-886C-57852CC8A120}",
 47            "/factory,{ceff45ee-c862-41de-aee2-a022c81eda92}"
 48          )
 49'''
 50
 51
 52[[rule.threat]]
 53framework = "MITRE ATT&CK"
 54[[rule.threat.technique]]
 55id = "T1566"
 56name = "Phishing"
 57reference = "https://attack.mitre.org/techniques/T1566/"
 58[[rule.threat.technique.subtechnique]]
 59id = "T1566.001"
 60name = "Spearphishing Attachment"
 61reference = "https://attack.mitre.org/techniques/T1566/001/"
 62
 63[[rule.threat.technique.subtechnique]]
 64id = "T1566.002"
 65name = "Spearphishing Link"
 66reference = "https://attack.mitre.org/techniques/T1566/002/"
 67
 68
 69
 70[rule.threat.tactic]
 71id = "TA0001"
 72name = "Initial Access"
 73reference = "https://attack.mitre.org/tactics/TA0001/"
 74
 75[[rule.threat]]
 76framework = "MITRE ATT&CK"
 77[[rule.threat.technique]]
 78id = "T1059"
 79name = "Command and Scripting Interpreter"
 80reference = "https://attack.mitre.org/techniques/T1059/"
 81[[rule.threat.technique.subtechnique]]
 82id = "T1059.001"
 83name = "PowerShell"
 84reference = "https://attack.mitre.org/techniques/T1059/001/"
 85
 86[[rule.threat.technique.subtechnique]]
 87id = "T1059.003"
 88name = "Windows Command Shell"
 89reference = "https://attack.mitre.org/techniques/T1059/003/"
 90[[rule.threat.technique.subtechnique]]
 91id = "T1059.005"
 92name = "Visual Basic"
 93reference = "https://attack.mitre.org/techniques/T1059/005/"
 94
 95
 96
 97[rule.threat.tactic]
 98id = "TA0002"
 99name = "Execution"
100reference = "https://attack.mitre.org/tactics/TA0002/"
101
102[[rule.threat]]
103framework = "MITRE ATT&CK"
104[[rule.threat.technique]]
105id = "T1218"
106name = "System Binary Proxy Execution"
107reference = "https://attack.mitre.org/techniques/T1218/"
108
109
110
111[rule.threat.tactic]
112id = "TA0005"
113name = "Defense Evasion"
114reference = "https://attack.mitre.org/tactics/TA0005/"