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Detection rules › Sigma

Potentially Suspicious Office Document Executed From Trusted Location

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

Detects the execution of an Office application that points to a document that is located in a trusted location. Attackers often used this to avoid macro security and execute their malicious code.

MITRE ATT&CK coverage

TacticTechniques
StealthT1202 Indirect Command Execution

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation

Rule body yaml

title: Potentially Suspicious Office Document Executed From Trusted Location
id: f99abdf0-6283-4e71-bd2b-b5c048a94743
status: test
description: Detects the execution of an Office application that points to a document that is located in a trusted location. Attackers often used this to avoid macro security and execute their malicious code.
references:
    - Internal Research
    - https://twitter.com/Max_Mal_/status/1633863678909874176
    - https://techcommunity.microsoft.com/t5/microsoft-365-blog/new-security-hardening-policies-for-trusted-documents/ba-p/3023465
    - https://twitter.com/_JohnHammond/status/1588155401752788994
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-06-21
modified: 2023-10-18
tags:
    - attack.stealth
    - attack.t1202
logsource:
    category: process_creation
    product: windows
detection:
    selection_parent:
        # Note: we add a parent shell to reduce FP. Add additional 3rd party shells that you might use
        ParentImage|endswith:
            - '\explorer.exe'
            - '\dopus.exe'
    selection_img:
        - Image|endswith:
              - '\EXCEL.EXE'
              - '\POWERPNT.EXE'
              - '\WINWORD.exe'
        - OriginalFileName:
              - 'Excel.exe'
              - 'POWERPNT.EXE'
              - 'WinWord.exe'
    selection_trusted_location:
        CommandLine|contains:
            # Note: these are the default locations. Admins/Users could add additional ones that you need to cover
            - '\AppData\Roaming\Microsoft\Templates'
            - '\AppData\Roaming\Microsoft\Word\Startup\'
            - '\Microsoft Office\root\Templates\'
            - '\Microsoft Office\Templates\'
    filter_main_dotx:
        # Note: We add this filter to avoid curious people clicking on template files
        CommandLine|endswith:
            - '.dotx'
            - '.xltx'
            - '.potx'
    condition: all of selection_* and not 1 of filter_main_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

all of selection_* and not 1 of filter_main_*

Stage 1: selection_parent

selection_parent:
    ParentImage|endswith:
        - '\explorer.exe'
        - '\dopus.exe'

Stage 2: selection_img

selection_img:
    - Image|endswith:
          - '\EXCEL.EXE'
          - '\POWERPNT.EXE'
          - '\WINWORD.exe'
    - OriginalFileName:
          - 'Excel.exe'
          - 'POWERPNT.EXE'
          - 'WinWord.exe'

Stage 3: selection_trusted_location

selection_trusted_location:
    CommandLine|contains:
        - '\AppData\Roaming\Microsoft\Templates'
        - '\AppData\Roaming\Microsoft\Word\Startup\'
        - '\Microsoft Office\root\Templates\'
        - '\Microsoft Office\Templates\'

Stage 4: not filter_main_dotx

filter_main_dotx:
    CommandLine|endswith:
        - '.dotx'
        - '.xltx'
        - '.potx'

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

FieldKindExcluded values
CommandLineends_with.dotx
CommandLineends_with.potx
CommandLineends_with.xltx

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
CommandLinematch
  • \AppData\Roaming\Microsoft\Templates
  • \AppData\Roaming\Microsoft\Word\Startup\
  • \Microsoft Office\Templates\
  • \Microsoft Office\root\Templates\
Imageends_with
  • \EXCEL.EXE corpus 18 (sigma 18)
  • \POWERPNT.EXE corpus 15 (sigma 15)
  • \WINWORD.exe corpus 20 (sigma 20)
OriginalFileNameeq
  • Excel.exe corpus 4 (sigma 3, elastic 1)
  • POWERPNT.EXE corpus 4 (sigma 3, elastic 1)
  • WinWord.exe corpus 6 (sigma 4, elastic 2)
ParentImageends_with
  • \dopus.exe
  • \explorer.exe corpus 13 (sigma 13)