Unsigned or Untrusted Process Execution via Installer

[rule]
description = """
Detects the execution of an unsigned or untrusted process via a shell by the macOS installer binary. This activity is
abnormal and may indicate an attempt to stage and execute a malicious payload.
"""
id = "752a2f7f-8d0c-4a7e-9665-ec948d14e947"
license = "Elastic License v2"
name = "Unsigned or Untrusted Process Execution via Installer"
os_list = ["macos"]
version = "1.0.5"

query = '''
process where event.type == "start" and 
 (process.code_signature.trusted == false or process.code_signature.exists == false) and 
 process.args_count == 1 and 
 process.parent.name in ("bash", "sh", "zsh") and
 process.Ext.effective_parent.executable like~ ("/usr/sbin/installer", "/System/Library/CoreServices/Installer.app/Contents/MacOS/Installer")
'''

min_endpoint_version = "8.11.0"
optional_actions = []
[[actions]]
action = "kill_process"
field = "process.entity_id"
state = 0

[[actions]]
action = "kill_process"
field = "process.parent.entity_id"
state = 0

[[threat]]
framework = "MITRE ATT&CK"
[[threat.technique]]
id = "T1546"
name = "Event Triggered Execution"
reference = "https://attack.mitre.org/techniques/T1546/"
[[threat.technique.subtechnique]]
id = "T1546.016"
name = "Installer Packages"
reference = "https://attack.mitre.org/techniques/T1546/016/"



[threat.tactic]
id = "TA0003"
name = "Persistence"
reference = "https://attack.mitre.org/tactics/TA0003/"

[internal]
min_endpoint_version = "8.11.0"