ATT&CK coverage › Technique

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

Adversaries may abuse Compiled HTML files (.chm) to conceal malicious code. CHM files are commonly distributed as part of the Microsoft HTML Help system. CHM files are compressed compilations of various content such as HTML documents, images, and scripting/web related programming languages such VBA, JScript, Java, and ActiveX. CHM content is displayed using underlying components of the Internet Explorer browser loaded by the HTML Help executable program (hh.exe).

Events covered

2 catalog events are tagged with this technique by at least one rule.

Provider	Event ID	Title
Sysmon	1	Process creation
Security-Auditing	4688	A new process has been created.

Authoring guide

Patterns shared across the 5 rules above: which fields they filter on, what specific values they look for, and what they exclude. Field names are normalized across vendors so Sigma's Image, Elastic's process.name, and Splunk's process_name collapse into one row. Each rule contributes at most once per row.

Fields filtered most (4 distinct)

The fields most rules look at when detecting this technique. The How column shows the operators authors use (eq, wildcard, regex_match, match) and how often each appears. Sample values are concrete examples to start from, not an exhaustive list.

Field	Rules	How	Sample values
`Image`	5	`ends_with` 5	`\hh.exe`, `\MSHTA.EXE`, `\rundll32.exe`, `\wmic.exe`, `\pwsh.exe`
`CommandLine`	4	`match` 4	`.chm`, `\onenoteofflinecache_files\`, `\exported\`, `https://`, `\\\\`
`OriginalFileName`	3	`eq` 3	`HH.exe`
`ParentImage`	2	`ends_with` 2	`\hh.exe`, `\onenote.exe`

Top indicator values (32 distinct)

Specific (field, operator, value) combinations the rules check for, ranked by how many rules under this technique use each one. The Corpus reach column counts how many rules across the entire catalog (any technique) check the same combination. High numbers point to widely-used indicators that are likely noisy on their own; combine them with another condition for useful signal. Blank means the combination is specific to rules under this technique.

Field	Kind	Value	Rules (here)	Corpus reach
`Image`	`ends_with`	`\hh.exe`	3	14
`OriginalFileName`	`eq`	`HH.exe`	3	5
`Image`	`ends_with`	`\cscript.exe`	2	64
`Image`	`ends_with`	`\wscript.exe`	2	64
`Image`	`ends_with`	`\cmd.exe`	2	92
`Image`	`ends_with`	`\pwsh.exe`	2	140
`Image`	`ends_with`	`\powershell.exe`	2	143
`CommandLine`	`match`	`.chm`	1	2
`Image`	`ends_with`	`\installutil.exe`	1	5
`Image`	`ends_with`	`\msiexec.exe`	1	21
`Image`	`ends_with`	`\CertReq.exe`	1	5
`ParentImage`	`ends_with`	`\hh.exe`	1
`Image`	`ends_with`	`\regsvr32.exe`	1	57
`Image`	`ends_with`	`\CertUtil.exe`	1
`Image`	`ends_with`	`\MSbuild.exe`	1
`Image`	`ends_with`	`\rundll32.exe`	1	76
`Image`	`ends_with`	`\wmic.exe`	1	37
`Image`	`ends_with`	`\MSHTA.EXE`	1
`Image`	`ends_with`	`\schtasks.exe`	1	45
`CommandLine`	`match`	`\exported\`	1

Rules under this technique

Every rule in the catalog tagged with this technique, grouped by vendor. Click a rule title for its full predicates, exclusions, and indicators.

Sigma 5 rules

HH.EXE Execution severity low, 1 event, 3 indicators, 0 exclusions
HTML Help HH.EXE Suspicious Child Process severity high, 2 events, 16 indicators, 0 exclusions
OneNote.EXE Execution of Malicious Embedded Scripts severity high, 2 events, 9 indicators, 0 exclusions
Remote CHM File Download/Execution Via HH.EXE severity high, 1 event, 5 indicators, 0 exclusions
Suspicious HH.EXE Execution severity high, 1 event, 8 indicators, 0 exclusions