Detection rules › Splunk
hh.exe Remote File Execution (Windows Event Log)
Adversaries may abuse Compiled HTML files (.chm) to conceal malicious code. CHM files are commonly distributed as part of the Microsoft HTML Help system. A custom CHM file containing embedded payloads could be delivered to a victim then triggered by User Execution. This use case detects hh.exe executions accessing a remote compiled HTML file. LOLBAS
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Stealth |
References
Telemetry coverage
| Provider | Record / event type |
|---|---|
| Security-Auditing | Event ID 4688: A new process has been created. |
Rule body
id: '17787.29931'
title: hh.exe Remote File Execution
description: 'Adversaries may abuse Compiled HTML files (.chm) to conceal malicious
code. CHM files are commonly distributed as part of the Microsoft HTML Help system.
A custom CHM file containing embedded payloads could be delivered to a victim then
triggered by User Execution. This use case detects hh.exe executions accessing a
remote compiled HTML file. LOLBAS Atomics T1218.001 Test #2'
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR
"<EventID>4688<" OR Type=Process) (TERM(hh) OR TERM(hh.exe)) | where match(process_name,
"(?i)hh\.exe") AND match(process, "(?i)\w+tps?://") | table _time, host, user process,
process_*, parent_* | bin span=1s | stats values(*) as * by _time, host '
techniques:
- defense-evasion:system binary proxy execution:compiled html file
technique_id:
- T1218.001
data_category:
- Windows event logs
references:
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.001/T1218.001.md#atomic-test-2---compiled-html-help-remote-payload
- https://www.ptsecurity.com/ww-en/analytics/pt-esc-threat-intelligence/higaisa-or-winnti-apt-41-backdoors-old-and-new/
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR "<EventID>4688<" OR Type=Process) (TERM(hh) OR TERM(hh.exe))
Stage 2: where
| where match(process_name, "(?i)hh\.exe") AND match(process, "(?i)\w+tps?://")
Stage 3: table
| table _time, host, user process, process_*, parent_*
Stage 4: bucket
| bin span=1s
Stage 5: stats
| stats values(*) as * by _time, host
Indicators
These rows show field, operator, and value matches.
| Field | Kind | Values | Search |
|---|---|---|---|
EventCode | eq |
| field:"EventID" kind:eq value:"4688" |
process | regex_match |
| field:"CommandLine" kind:regex_match |
process_name | regex_match |
| field:"process_name" kind:regex_match |
Search terms
These SPL tokens match against raw event text.
| Stage | Term |
|---|---|
| 1 | "<EventID>4688<" |
| 1 | hh |
| 1 | hh.exe |