sigma-rules/rules/windows/persistence_powershell_exch_mailbox_activesync_add_device.toml

[metadata]
creation_date = "2020/12/15"
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"]
description = """
Identifies the use of the Exchange PowerShell cmdlet, Set-CASMailbox, to add a new ActiveSync allowed device.
Adversaries may target user email to collect sensitive information.
"""
false_positives = ["Legitimate exchange system administration activity."]
from = "now-9m"
index = ["logs-endpoint.events.*", "winlogbeat-*", "logs-windows.*", "endgame-*"]
language = "eql"
license = "Elastic License v2"
name = "New ActiveSyncAllowedDeviceID Added via PowerShell"
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.volexity.com/blog/2020/12/14/dark-halo-leverages-solarwinds-compromise-to-breach-organizations/",
    "https://docs.microsoft.com/en-us/powershell/module/exchange/set-casmailbox?view=exchange-ps",
]
risk_score = 47
rule_id = "ce64d965-6cb0-466d-b74f-8d2c76f47f05"
severity = "medium"
tags = ["Elastic", "Host", "Windows", "Threat Detection", "Persistence", "Elastic Endgame"]
timestamp_override = "event.ingested"
type = "eql"

query = '''
process where host.os.type == "windows" and event.type == "start" and
  process.name: ("powershell.exe", "pwsh.exe", "powershell_ise.exe") and process.args : "Set-CASMailbox*ActiveSyncAllowedDeviceIDs*"
'''


[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1098"
name = "Account Manipulation"
reference = "https://attack.mitre.org/techniques/T1098/"
[[rule.threat.technique.subtechnique]]
id = "T1098.002"
name = "Additional Email Delegate Permissions"
reference = "https://attack.mitre.org/techniques/T1098/002/"



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