Outlook EnableUnsafeClientMailRules Setting Enabled

Status: test
Severity: high
Log source: category process_creation, product windows
Author: Markus Neis, Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects an attacker trying to enable the outlook security setting "EnableUnsafeClientMailRules" which allows outlook to run applications or execute macros

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059` Command and Scripting Interpreter
Stealth	`T1202` Indirect Command Execution

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: Outlook EnableUnsafeClientMailRules Setting Enabled
id: 55f0a3a1-846e-40eb-8273-677371b8d912
related:
    - id: 6763c6c8-bd01-4687-bc8d-4fa52cf8ba08 # Registry variation
      type: similar
status: test
description: Detects an attacker trying to enable the outlook security setting "EnableUnsafeClientMailRules" which allows outlook to run applications or execute macros
references:
    - https://www.fireeye.com/blog/threat-research/2018/12/overruled-containing-a-potentially-destructive-adversary.html
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=44
    - https://support.microsoft.com/en-us/topic/how-to-control-the-rule-actions-to-start-an-application-or-run-a-macro-in-outlook-2016-and-outlook-2013-e4964b72-173c-959d-5d7b-ead562979048
author: Markus Neis, Nasreddine Bencherchali (Nextron Systems)
date: 2018-12-27
modified: 2023-02-09
tags:
    - attack.execution
    - attack.stealth
    - attack.t1059
    - attack.t1202
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        CommandLine|contains: '\Outlook\Security\EnableUnsafeClientMailRules'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    CommandLine|contains: '\Outlook\Security\EnableUnsafeClientMailRules'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`\Outlook\Security\EnableUnsafeClientMailRules`	`field:"CommandLine" kind:match value:"\Outlook\Security\EnableUnsafeClientMailRules"`