sigma-rules/rules/windows/initial_access_suspicious_ms_exchange_process.toml

[metadata]
creation_date = "2021/03/04"
integration = ["endpoint", "windows"]
maturity = "production"
min_stack_comments = "New fields added: required_fields, related_integrations, setup"
min_stack_version = "8.3.0"
updated_date = "2023/03/06"

[rule]
author = ["Elastic", "Austin Songer"]
description = """
Identifies suspicious processes being spawned by the Microsoft Exchange Server Unified Messaging (UM) service. This
activity has been observed exploiting CVE-2021-26857.
"""
false_positives = [
    """
    Legitimate processes may be spawned from the Microsoft Exchange Server Unified Messaging (UM) service. If known
    processes are causing false positives, they can be exempted from the rule.
    """,
]
from = "now-9m"
index = ["logs-endpoint.events.*", "winlogbeat-*", "logs-windows.*", "endgame-*"]
language = "eql"
license = "Elastic License v2"
name = "Microsoft Exchange Server UM Spawning Suspicious Processes"
note = """## Setup

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define `event.ingested` and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.
"""
references = [
    "https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers",
    "https://www.volexity.com/blog/2021/03/02/active-exploitation-of-microsoft-exchange-zero-day-vulnerabilities",
]
risk_score = 47
rule_id = "483c4daf-b0c6-49e0-adf3-0bfa93231d6b"
severity = "medium"
tags = ["Elastic", "Host", "Windows", "Threat Detection", "Initial Access", "Elastic Endgame"]
timestamp_override = "event.ingested"
type = "eql"

query = '''
process where host.os.type == "windows" and event.type == "start" and
  process.parent.name : ("UMService.exe", "UMWorkerProcess.exe") and
    not process.executable :
              ("?:\\Windows\\System32\\werfault.exe",
               "?:\\Windows\\System32\\wermgr.exe",
               "?:\\Program Files\\Microsoft\\Exchange Server\\V??\\Bin\\UMWorkerProcess.exe",
               "D:\\Exchange 2016\\Bin\\UMWorkerProcess.exe",
               "E:\\ExchangeServer\\Bin\\UMWorkerProcess.exe")
'''


[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1190"
name = "Exploit Public-Facing Application"
reference = "https://attack.mitre.org/techniques/T1190/"


[rule.threat.tactic]
id = "TA0001"
name = "Initial Access"
reference = "https://attack.mitre.org/tactics/TA0001/"