Unusual Process Extension

[metadata]
creation_date = "2023/08/23"
integration = ["endpoint"]
maturity = "production"
updated_date = "2024/05/21"

[rule]
author = ["Elastic"]
building_block_type = "default"
description = "Identifies processes running with unusual extensions that are not typically valid for Windows executables.\n"
from = "now-119m"
index = ["logs-endpoint.events.process-*"]
interval = "60m"
language = "eql"
license = "Elastic License v2"
name = "Unusual Process Extension"
risk_score = 21
rule_id = "800e01be-a7a4-46d0-8de9-69f3c9582b44"
severity = "low"
tags = [
    "Domain: Endpoint",
    "OS: Windows",
    "Use Case: Threat Detection",
    "Tactic: Defense Evasion",
    "Data Source: Elastic Defend",
    "Rule Type: BBR",
]
timestamp_override = "event.ingested"
type = "eql"

query = '''
process where host.os.type == "windows" and event.type == "start" and
  process.executable : "?*" and 
  not process.name : ("*.exe", "*.com", "*.scr", "*.tmp", "*.dat") and
  not process.executable : 
    (
      "MemCompression",
      "Registry",
      "vmmem",
      "vmmemWSL",
      "?:\\Program Files\\Dell\\SupportAssistAgent\\*.p5x",
      "?:\\Program Files\\Docker\\Docker\\com.docker.service",
      "?:\\Users\\*\\AppData\\Local\\Intel\\AGS\\Libs\\AGSRunner.bin",
      "\\Device\\Mup\\*\\Software Management\\Select.Html.dep",
      "?:\\DJJApplications\\MedicalRecords\\bin\\Select.Html.dep",
      "?:\\ProgramData\\Software Management\\Select.Html.dep",
      "?:\\Program Files (x86)\\EnCase Applications\\Examiner Service\\EnCase64\\enhkey.dll",
      "?:\\Program Files (x86)\\Panda Security\\WAC\\PSNAEInj64.dll",
      "?:\\Program Files (x86)\\Johnson Controls\\LicenseActivator\\crp32002.ngn"
    ) and
  not (
    (process.name : "C9632CF058AE4321B6B0B5EA39B710FE" and process.code_signature.subject_name == "Dell Inc") or
    (process.name : "*.upd" and process.code_signature.subject_name == "Bloomberg LP") or
    (process.name: "FD552E21-686E-413C-931D-3B82A9D29F3B" and process.code_signature.subject_name: "Adobe Inc.") or
    (process.name: "3B91051C-AE82-43C9-BCEF-0309CD2DD9EB" and process.code_signature.subject_name: "McAfee, LLC") or
    (process.name: "soffice.bin" and process.code_signature.subject_name: "The Document Foundation") or
    (process.name: ("VeeamVixProxy_*", "{????????-????-????-????-????????????}") and process.code_signature.subject_name: "Veeam Software Group GmbH") or
    (process.name: "1cv8p64.bin" and process.code_signature.subject_name: "LLC 1C-Soft") or
    (process.name: "AGSRunner.bin" and process.code_signature.subject_name: "Intel Corporation")
  )
'''


[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1036"
name = "Masquerading"
reference = "https://attack.mitre.org/techniques/T1036/"
[[rule.threat.technique.subtechnique]]
id = "T1036.008"
name = "Masquerade File Type"
reference = "https://attack.mitre.org/techniques/T1036/008/"



[rule.threat.tactic]
id = "TA0005"
name = "Defense Evasion"
reference = "https://attack.mitre.org/tactics/TA0005/"