Remote CHM File Download/Execution Via HH.EXE

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

Detects the usage of "hh.exe" to execute/download remotely hosted ".chm" files.

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1218.001` System Binary Proxy Execution: Compiled HTML File

Telemetry coverage

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

Rule body

title: Remote CHM File Download/Execution Via HH.EXE
id: f57c58b3-ee69-4ef5-9041-455bf39aaa89
status: test
description: Detects the usage of "hh.exe" to execute/download remotely hosted ".chm" files.
references:
    - https://www.splunk.com/en_us/blog/security/follina-for-protocol-handlers.html
    - https://github.com/redcanaryco/atomic-red-team/blob/1cf4dd51f83dcb0ebe6ade902d6157ad2dbc6ac8/atomics/T1218.001/T1218.001.md
    - https://www.zscaler.com/blogs/security-research/unintentional-leak-glimpse-attack-vectors-apt37
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-09-29
modified: 2024-01-31
tags:
    - attack.stealth
    - attack.t1218.001
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - OriginalFileName: 'HH.exe'
        - Image|endswith: '\hh.exe'
    selection_cli:
        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:
    - OriginalFileName: 'HH.exe'
    - Image|endswith: '\hh.exe'

Stage 2: `selection_cli`

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

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`\\\\` corpus 6 (sigma 5, splunk 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	`\hh.exe` corpus 15 (sigma 15)	`field:"Image" kind:ends_with value:"\hh.exe"`
`OriginalFileName`	eq	`HH.exe` corpus 11 (sigma 5, splunk 4, elastic 2)	`field:"OriginalFileName" kind:eq value:"HH.exe"`

Remote CHM File Download/Execution Via HH.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`