Suspicious Explorer Child Process

  1[metadata]
  2creation_date = "2020/10/29"
  3integration = ["endpoint", "windows"]
  4maturity = "production"
  5updated_date = "2024/05/21"
  6
  7[rule]
  8author = ["Elastic"]
  9description = """
 10Identifies a suspicious Windows explorer child process. Explorer.exe can be abused to launch malicious scripts or
 11executables from a trusted parent process.
 12"""
 13from = "now-9m"
 14index = ["logs-endpoint.events.process-*", "winlogbeat-*", "logs-windows.sysmon_operational-*", "endgame-*"]
 15language = "eql"
 16license = "Elastic License v2"
 17name = "Suspicious Explorer Child Process"
 18risk_score = 47
 19rule_id = "9a5b4e31-6cde-4295-9ff7-6be1b8567e1b"
 20setup = """## Setup
 21
 22If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2,
 23events will not define `event.ingested` and default fallback for EQL rules was not added until version 8.2.
 24Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate
 25`event.ingested` to @timestamp.
 26For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html
 27"""
 28severity = "medium"
 29tags = [
 30    "Domain: Endpoint",
 31    "OS: Windows",
 32    "Use Case: Threat Detection",
 33    "Tactic: Initial Access",
 34    "Tactic: Defense Evasion",
 35    "Tactic: Execution",
 36    "Data Source: Elastic Endgame",
 37    "Data Source: Elastic Defend",
 38    "Data Source: Sysmon",
 39]
 40timestamp_override = "event.ingested"
 41type = "eql"
 42
 43query = '''
 44process where host.os.type == "windows" and event.type == "start" and
 45  (
 46   process.name : ("cscript.exe", "wscript.exe", "powershell.exe", "rundll32.exe", "cmd.exe", "mshta.exe", "regsvr32.exe") or
 47   process.pe.original_file_name in ("cscript.exe", "wscript.exe", "PowerShell.EXE", "RUNDLL32.EXE", "Cmd.Exe", "MSHTA.EXE", "REGSVR32.EXE")
 48  ) and
 49  /* Explorer started via DCOM */
 50  process.parent.name : "explorer.exe" and process.parent.args : "-Embedding" and
 51  not process.parent.args:
 52          (
 53            /* Noisy CLSID_SeparateSingleProcessExplorerHost Explorer COM Class IDs   */
 54            "/factory,{5BD95610-9434-43C2-886C-57852CC8A120}",
 55            "/factory,{ceff45ee-c862-41de-aee2-a022c81eda92}"
 56          )
 57'''
 58
 59
 60[[rule.threat]]
 61framework = "MITRE ATT&CK"
 62[[rule.threat.technique]]
 63id = "T1566"
 64name = "Phishing"
 65reference = "https://attack.mitre.org/techniques/T1566/"
 66[[rule.threat.technique.subtechnique]]
 67id = "T1566.001"
 68name = "Spearphishing Attachment"
 69reference = "https://attack.mitre.org/techniques/T1566/001/"
 70
 71[[rule.threat.technique.subtechnique]]
 72id = "T1566.002"
 73name = "Spearphishing Link"
 74reference = "https://attack.mitre.org/techniques/T1566/002/"
 75
 76
 77
 78[rule.threat.tactic]
 79id = "TA0001"
 80name = "Initial Access"
 81reference = "https://attack.mitre.org/tactics/TA0001/"
 82[[rule.threat]]
 83framework = "MITRE ATT&CK"
 84[[rule.threat.technique]]
 85id = "T1059"
 86name = "Command and Scripting Interpreter"
 87reference = "https://attack.mitre.org/techniques/T1059/"
 88[[rule.threat.technique.subtechnique]]
 89id = "T1059.001"
 90name = "PowerShell"
 91reference = "https://attack.mitre.org/techniques/T1059/001/"
 92
 93[[rule.threat.technique.subtechnique]]
 94id = "T1059.003"
 95name = "Windows Command Shell"
 96reference = "https://attack.mitre.org/techniques/T1059/003/"
 97
 98[[rule.threat.technique.subtechnique]]
 99id = "T1059.005"
100name = "Visual Basic"
101reference = "https://attack.mitre.org/techniques/T1059/005/"
102
103
104
105[rule.threat.tactic]
106id = "TA0002"
107name = "Execution"
108reference = "https://attack.mitre.org/tactics/TA0002/"
109[[rule.threat]]
110framework = "MITRE ATT&CK"
111[[rule.threat.technique]]
112id = "T1218"
113name = "System Binary Proxy Execution"
114reference = "https://attack.mitre.org/techniques/T1218/"
115
116
117[rule.threat.tactic]
118id = "TA0005"
119name = "Defense Evasion"
120reference = "https://attack.mitre.org/tactics/TA0005/"