Potential Arbitrary File Download Using Office Application

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

Detects potential arbitrary file download using a Microsoft Office application

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1202` Indirect Command Execution

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

title: Potential Arbitrary File Download Using Office Application
id: 4ae3e30b-b03f-43aa-87e3-b622f4048eed
related:
    - id: 0c79148b-118e-472b-bdb7-9b57b444cc19
      type: obsolete
status: test
description: Detects potential arbitrary file download using a Microsoft Office application
references:
    - https://lolbas-project.github.io/lolbas/OtherMSBinaries/Winword/
    - https://lolbas-project.github.io/lolbas/OtherMSBinaries/Powerpnt/
    - https://lolbas-project.github.io/lolbas/OtherMSBinaries/Excel/
    - https://medium.com/@reegun/unsanitized-file-validation-leads-to-malicious-payload-download-via-office-binaries-202d02db7191
author: Nasreddine Bencherchali (Nextron Systems), Beyu Denis, oscd.community
date: 2022-05-17
modified: 2023-06-22
tags:
    - attack.stealth
    - attack.t1202
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith:
              - '\EXCEL.EXE'
              - '\POWERPNT.EXE'
              - '\WINWORD.exe'
        - OriginalFileName:
              - 'Excel.exe'
              - 'POWERPNT.EXE'
              - 'WinWord.exe'
    selection_http:
        CommandLine|contains:
            - 'http://'
            - 'https://'
    condition: all of selection_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_img`

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

Stage 2: `selection_http`

selection_http:
    CommandLine|contains:
        - 'http://'
        - 'https://'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`http://` corpus 23 (sigma 18, elastic 2, kusto 2, splunk 1) `https://` corpus 23 (sigma 18, elastic 2, kusto 2, splunk 1)	`field:"CommandLine" kind:match`
`Image`	ends_with	`\EXCEL.EXE` corpus 16 (sigma 16) `\POWERPNT.EXE` corpus 14 (sigma 14) `\WINWORD.exe` corpus 17 (sigma 17)	`field:"Image" kind:ends_with`
`OriginalFileName`	eq	`Excel.exe` corpus 4 (sigma 3, elastic 1) `POWERPNT.EXE` corpus 4 (sigma 3, elastic 1) `WinWord.exe` corpus 6 (sigma 4, elastic 2)	`field:"OriginalFileName" kind:eq`

Potential Arbitrary File Download Using Office Application

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection_img

Stage 2: selection_http

Indicators

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_http`