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 | T1218.001 System Binary Proxy Execution: Compiled HTML File |
References
Event coverage
| Provider | Event | Title |
|---|---|---|
| Security-Auditing | Event ID 4688 | A new process has been created. |
Rule body yaml
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
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.
| Field | Kind | Values |
|---|---|---|
EventCode | eq |
|
process | match |
|
process_name | match |
|
Search terms
Bare-string tokens in the SPL search body. Splunk matches each token against _raw (the untyped raw event text) anywhere it appears, not against a specific field. These don't surface in the Indicators table because they aren't predicates on a known field.
| Stage | Term |
|---|---|
| 1 | TERM |
| 1 | "<EventID>4688<" |
| 1 | TERM |
| 1 | hh |
| 1 | TERM |
| 1 | hh.exe |