Detection rules › Splunk
hh.exe Remote File Execution (Sysmon)
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 |
|---|---|---|
| Sysmon | Event ID 1 | Process creation |
Rule body yaml
id: '17787.30036'
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_sysmon` (TERM(EventCode=1) OR "<EventID>1<")
(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 Sysmon
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_sysmon` (TERM(EventCode=1) OR "<EventID>1<") (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>1<" |
| 1 | TERM |
| 1 | hh |
| 1 | TERM |
| 1 | hh.exe |