Suspicious Execution from a Mounted Device

  1[metadata]
  2creation_date = "2021/05/28"
  3integration = ["endpoint", "windows"]
  4maturity = "production"
  5updated_date = "2024/05/21"
  6
  7[rule]
  8author = ["Elastic"]
  9description = """
 10Identifies when a script interpreter or signed binary is launched via a non-standard working directory. An attacker may
 11use this technique to evade defenses.
 12"""
 13from = "now-9m"
 14index = ["winlogbeat-*", "logs-endpoint.events.process-*", "logs-windows.sysmon_operational-*"]
 15language = "eql"
 16license = "Elastic License v2"
 17name = "Suspicious Execution from a Mounted Device"
 18references = [
 19    "https://www.microsoft.com/security/blog/2021/05/27/new-sophisticated-email-based-attack-from-nobelium/",
 20    "https://www.volexity.com/blog/2021/05/27/suspected-apt29-operation-launches-election-fraud-themed-phishing-campaigns/",
 21]
 22risk_score = 47
 23rule_id = "8a1d4831-3ce6-4859-9891-28931fa6101d"
 24setup = """## Setup
 25
 26If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2,
 27events will not define `event.ingested` and default fallback for EQL rules was not added until version 8.2.
 28Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate
 29`event.ingested` to @timestamp.
 30For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html
 31"""
 32severity = "medium"
 33tags = [
 34    "Domain: Endpoint",
 35    "OS: Windows",
 36    "Use Case: Threat Detection",
 37    "Tactic: Defense Evasion",
 38    "Tactic: Execution",
 39    "Data Source: Elastic Defend",
 40    "Data Source: Sysmon",
 41]
 42timestamp_override = "event.ingested"
 43type = "eql"
 44
 45query = '''
 46process where host.os.type == "windows" and event.type == "start" and process.executable : "C:\\*" and
 47  (process.working_directory : "?:\\" and not process.working_directory: "C:\\") and
 48  process.parent.name : "explorer.exe" and
 49  process.name : ("rundll32.exe", "mshta.exe", "powershell.exe", "pwsh.exe", "cmd.exe", "regsvr32.exe",
 50                  "cscript.exe", "wscript.exe")
 51'''
 52
 53
 54[[rule.threat]]
 55framework = "MITRE ATT&CK"
 56[[rule.threat.technique]]
 57id = "T1218"
 58name = "System Binary Proxy Execution"
 59reference = "https://attack.mitre.org/techniques/T1218/"
 60[[rule.threat.technique.subtechnique]]
 61id = "T1218.005"
 62name = "Mshta"
 63reference = "https://attack.mitre.org/techniques/T1218/005/"
 64
 65[[rule.threat.technique.subtechnique]]
 66id = "T1218.010"
 67name = "Regsvr32"
 68reference = "https://attack.mitre.org/techniques/T1218/010/"
 69
 70[[rule.threat.technique.subtechnique]]
 71id = "T1218.011"
 72name = "Rundll32"
 73reference = "https://attack.mitre.org/techniques/T1218/011/"
 74
 75
 76
 77[rule.threat.tactic]
 78id = "TA0005"
 79name = "Defense Evasion"
 80reference = "https://attack.mitre.org/tactics/TA0005/"
 81[[rule.threat]]
 82framework = "MITRE ATT&CK"
 83[[rule.threat.technique]]
 84id = "T1059"
 85name = "Command and Scripting Interpreter"
 86reference = "https://attack.mitre.org/techniques/T1059/"
 87[[rule.threat.technique.subtechnique]]
 88id = "T1059.001"
 89name = "PowerShell"
 90reference = "https://attack.mitre.org/techniques/T1059/001/"
 91
 92[[rule.threat.technique.subtechnique]]
 93id = "T1059.003"
 94name = "Windows Command Shell"
 95reference = "https://attack.mitre.org/techniques/T1059/003/"
 96
 97
 98
 99[rule.threat.tactic]
100id = "TA0002"
101name = "Execution"
102reference = "https://attack.mitre.org/tactics/TA0002/"