Arbitrary File Download Via MSOHTMED.EXE

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

Detects usage of "MSOHTMED" to download arbitrary files

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1218` System Binary Proxy Execution

Telemetry coverage

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

Rule body

title: Arbitrary File Download Via MSOHTMED.EXE
id: 459f2f98-397b-4a4a-9f47-6a5ec2f1c69d
status: test
description: Detects usage of "MSOHTMED" to download arbitrary files
references:
    - https://github.com/LOLBAS-Project/LOLBAS/pull/238/files
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-08-19
modified: 2023-11-09
tags:
    - attack.execution
    - attack.stealth
    - attack.t1218
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\MSOHTMED.exe'
        - OriginalFileName: 'MsoHtmEd.exe'
    selection_cli:
        CommandLine|contains:
            - 'ftp://'
            - 'http://'
            - 'https://'
    condition: all of selection_*
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_img`

selection_img:
    - Image|endswith: '\MSOHTMED.exe'
    - OriginalFileName: 'MsoHtmEd.exe'

Stage 2: `selection_cli`

selection_cli:
    CommandLine|contains:
        - 'ftp://'
        - 'http://'
        - 'https://'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`ftp://` corpus 13 (sigma 11, elastic 1, kusto 1) `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	`\MSOHTMED.exe`	`field:"Image" kind:ends_with value:"\MSOHTMED.exe"`
`OriginalFileName`	eq	`MsoHtmEd.exe`	`field:"OriginalFileName" kind:eq value:"MsoHtmEd.exe"`

Arbitrary File Download Via MSOHTMED.EXE

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection_img

Stage 2: selection_cli

Indicators

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_cli`