Detection rules › Sigma

Suspicious Binary In User Directory Spawned From Office Application

Status
test
Severity
high
Log source
product windows, category process_creation
Author
Jason Lynch
Source
github.com/SigmaHQ/sigma

Detects an executable in the users directory started from one of the Microsoft Office suite applications (Word, Excel, PowerPoint, Publisher, Visio)

MITRE ATT&CK coverage

Event coverage

Rule body yaml

title: Suspicious Binary In User Directory Spawned From Office Application
id: aa3a6f94-890e-4e22-b634-ffdfd54792cc
status: test
description: Detects an executable in the users directory started from one of the Microsoft Office suite applications (Word, Excel, PowerPoint, Publisher, Visio)
references:
    - https://blog.morphisec.com/fin7-not-finished-morphisec-spots-new-campaign
    - https://www.virustotal.com/gui/file/23160972c6ae07f740800fa28e421a81d7c0ca5d5cab95bc082b4a986fbac57
author: Jason Lynch
date: 2019-04-02
modified: 2023-02-04
tags:
    - attack.execution
    - attack.t1204.002
    - attack.g0046
    - car.2013-05-002
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        ParentImage|endswith:
            - '\WINWORD.EXE'
            - '\EXCEL.EXE'
            - '\POWERPNT.exe'
            - '\MSPUB.exe'
            - '\VISIO.exe'
            - '\MSACCESS.exe'
            - '\EQNEDT32.exe'
            # - '\OUTLOOK.EXE' too many FPs
        Image|startswith: 'C:\users\'
        Image|endswith: '.exe'
    filter:
        Image|endswith: '\Teams.exe'
    condition: selection and not filter
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection and not filter

Stage 1: selection

selection:
    ParentImage|endswith:
        - '\WINWORD.EXE'
        - '\EXCEL.EXE'
        - '\POWERPNT.exe'
        - '\MSPUB.exe'
        - '\VISIO.exe'
        - '\MSACCESS.exe'
        - '\EQNEDT32.exe'
    Image|startswith: 'C:\users\'
    Image|endswith: '.exe'

Stage 2: not filter

filter:
    Image|endswith: '\Teams.exe'

Exclusions

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

FieldKindExcluded values
Imageends_with\Teams.exe

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
Imageends_with
  • .exe corpus 4 (sigma 4)
Imagestarts_with
  • C:\users\
ParentImageends_with
  • \EQNEDT32.exe corpus 5 (sigma 5)
  • \EXCEL.EXE corpus 8 (sigma 8)
  • \MSACCESS.exe corpus 4 (sigma 4)
  • \MSPUB.exe corpus 4 (sigma 4)
  • \POWERPNT.exe corpus 6 (sigma 6)
  • \VISIO.exe corpus 4 (sigma 4)
  • \WINWORD.EXE corpus 10 (sigma 10)