T1218.001: Compiled HTML File

T1218.001: Compiled HTML File describes 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. (Citation: Microsoft HTML Help May 2018) CHM content is displayed using underlying components of the Internet Explorer browser (Citation: Microsoft HTML Help ActiveX) loaded by the HTML Help ...

Executive priority

T1218.001: Compiled HTML File is an official MITRE ATT&CK technique. Glexia treats it as defensive behavior context for prioritizing monitoring, control validation, and response planning without using the object by itself as an attribution claim.

Technical view

Security teams should validate T1218.001: Compiled HTML File by reviewing the official ATT&CK relationships, mapped tactics (stealth), supported platforms (Windows), and available local telemetry before making detection or mitigation decisions.

Likely telemetry

Official ATT&CK relationships and object metadata
Network, endpoint, and security-tool telemetry

Detection direction

Validate whether T1218.001: Compiled HTML File appears in your detection coverage and tabletop scenarios.
Use the object to align executive risk language with SOC, incident response, and detection engineering work.
Do not treat ATT&CK relationship context as attribution without corroborating evidence.

Mitigation priorities

Map the object to existing controls and identify missing telemetry or response ownership.
Prioritize mitigations that reduce exposure on the listed platforms and tactics.
Review adjacent ATT&CK relationships before changing policy, detections, or reporting language.

Additional notes and limits

Baseline Glexia take generated from the official MITRE ATT&CK STIX object, source hash, tactics, platforms, and detection fields. It is safe to replace with a richer model-generated take for the same source hash later.

This baseline take is source-grounded and schema-validated, but it does not include environment-specific telemetry, incident evidence, or threat-intelligence corroboration.

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Official MITRE ATT&CK definition

Compiled HTML File

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. [1] CHM content is displayed using underlying components of the Internet Explorer browser [2] loaded by the HTML Help executable program (hh.exe). [3]

A custom CHM file containing embedded payloads could be delivered to a victim then triggered by User Execution. CHM execution may also bypass application application control on older and/or unpatched systems that do not account for execution of binaries through hh.exe. [4] [5]

View the same entry on attack.mitre.org (MITRE-hosted reference; in-page links above use the Glexia ATT&CK library.)

Glexia analysis

How security teams should use this page

Treat this object as behavior context, not an attribution claim. Validate the related groups, software, data sources, and mitigations against official ATT&CK relationships and your own telemetry before making control-coverage decisions.

ATT&CK relationship table

Related techniques

This mirrors the MITRE pattern of making group, software, campaign, and technique relationships scannable. Relationship notes come from mirrored ATT&CK relationship text when available.

Filter related techniques2 rows

Domain	ID	Name	Relationship / procedure
Enterprise	T1218	System Binary Proxy Execution	This object subtechnique of System Binary Proxy Execution.
Enterprise	T1223	Compiled HTML File	Compiled HTML File revoked by this object.

Associated objects

Groups, software, and campaigns

G0082: APT38

APT38 is a North Korean state-sponsored threat group that specializes in financial cyber operations; it has been attributed to the Reconnaissance General Bureau.[1] Active since at least 2014, APT38 has targeted banks, financial institutions, casinos, cryptocurrency exchanges, SWIFT system endpoints, and ATMs in at least 38 countries worldwide. Significant operations include the 2016 Bank of Bangladesh heist, during which APT38 stole $81 million, as well as attacks against Bancomext [2] and Banco de Chile [2]; some of their attacks have been destructive.[1][2][3][4]

North Korean group definitions are known to have significant overlap, and some security researchers report all North Korean state-sponsored cyber activity under the name Lazarus Group instead of tracking clusters or subgroups.

G0096: APT41

APT41 is a threat group that researchers have assessed as Chinese state-sponsored espionage group that also conducts financially-motivated operations. Active since at least 2012, APT41 has been observed targeting various industries, including but not limited to healthcare, telecom, technology, finance, education, retail and video game industries in 14 countries.[1] Notable behaviors include using a wide range of malware and tools to complete mission objectives. APT41 overlaps at least partially with public reporting on groups including BARIUM and Winnti Group.[2][3]

G0049: OilRig

OilRig is a suspected Iranian threat group that has targeted Middle Eastern and international victims since at least 2014. The group has targeted a variety of sectors, including financial, government, energy, chemical, and telecommunications. It appears the group carries out supply chain attacks, leveraging the trust relationship between organizations to attack their primary targets. The group works on behalf of the Iranian government based on infrastructure details that contain references to Iran, use of Iranian infrastructure, and targeting that aligns with nation-state interests.[1][2][3][4][5][6][7]

G0070: Dark Caracal

Dark Caracal is threat group that has been attributed to the Lebanese General Directorate of General Security (GDGS) and has operated since at least 2012. [1]

G0091: Silence

Silence is a financially motivated threat actor targeting financial institutions in different countries. The group was first seen in June 2016. Their main targets reside in Russia, Ukraine, Belarus, Azerbaijan, Poland and Kazakhstan. They compromised various banking systems, including the Russian Central Bank's Automated Workstation Client, ATMs, and card processing.[1][2]

S0373: Astaroth

Astaroth is a Trojan and information stealer known to affect companies in Europe, Brazil, and throughout Latin America. It has been known publicly since at least late 2017. [1][2][3]

Windows

Relationship explorer

All related ATT&CK context

mitigates · MitigationM1021: Restrict Web-Based ContentEnterprise mitigates · MitigationM1038: Execution PreventionEnterprise uses · GroupG0082: APT38Enterprise uses · GroupG0096: APT41Enterprise uses · GroupG0049: OilRigEnterprise uses · GroupG0070: Dark CaracalEnterprise uses · GroupG0091: SilenceEnterprise uses · MalwareS0373: AstarothEnterprise subtechnique of · TechniqueT1218: System Binary Proxy ExecutionEnterprise detects · Detection StrategyDET0342: Detection of Suspicious Compiled HTML File Execution via hh.exeEnterprise revoked by · TechniqueT1223: Compiled HTML FileEnterprise

Mitigations

Mitigation direction

M1021: Restrict Web-Based Content

Restricting web-based content involves enforcing policies and technologies that limit access to potentially malicious websites, unsafe downloads, and unauthorized browser behaviors. This can include URL filtering, download restrictions, script blocking, and extension control to protect against exploitation, phishing, and malware delivery. This mitigation can be implemented through the following measures:

Deploy Web Proxy Filtering:

- Use solutions to filter web traffic based on categories, reputation, and content types. - Enforce policies that block unsafe websites or file types at the gateway level.

Enable DNS-Based Filtering:

- Implement tools to restrict access to domains associated with malware or phishing campaigns. - Use public DNS filtering services to enhance protection.

Enforce Content Security Policies (CSP):

- Configure CSP headers on internal and external web applications to restrict script execution, iframe embedding, and cross-origin requests.

Control Browser Features:

- Disable unapproved browser features like automatic downloads, developer tools, or unsafe scripting. - Enforce policies through tools like Group Policy Management to control browser settings.

Monitor and Alert on Web-Based Threats:

- Use SIEM tools to collect and analyze web proxy logs for signs of anomalous or malicious activity. - Configure alerts for access attempts to blocked domains or repeated file download failures.

M1038: Execution Prevention

Prevent the execution of unauthorized or malicious code on systems by implementing application control, script blocking, and other execution prevention mechanisms. This ensures that only trusted and authorized code is executed, reducing the risk of malware and unauthorized actions. This mitigation can be implemented through the following measures:

Application Control:

- Use Case: Use tools like AppLocker or Windows Defender Application Control (WDAC) to create whitelists of authorized applications and block unauthorized ones. On Linux, use tools like SELinux or AppArmor to define mandatory access control policies for application execution. - Implementation: Allow only digitally signed or pre-approved applications to execute on servers and endpoints. (e.g., `New-AppLockerPolicy -PolicyType Enforced -FilePath "C:\Policies\AppLocker.xml"`)

Script Blocking:

- Use Case: Use script control mechanisms to block unauthorized execution of scripts, such as PowerShell or JavaScript. Web Browsers: Use browser extensions or settings to block JavaScript execution from untrusted sources. - Implementation: Configure PowerShell to enforce Constrained Language Mode for non-administrator users. (e.g., `Set-ExecutionPolicy AllSigned`)

Executable Blocking:

- Use Case: Prevent execution of binaries from suspicious locations, such as `%TEMP%` or `%APPDATA%` directories. - Implementation: Block execution of `.exe`, `.bat`, or `.ps1` files from user-writable directories.

Dynamic Analysis Prevention: - Use Case: Use behavior-based execution prevention tools to identify and block malicious activity in real time. - Implemenation: Employ EDR solutions that analyze runtime behavior and block suspicious code execution.

Change history

Object version and sync metadata

The fields below describe the current mirrored snapshot. When Glexia retains multiple ATT&CK source imports, you can open the table to compare the same object across releases (hashes and MITRE timestamps). For MITRE’s own release notes and roadmap, see ATT&CK resources — Updates.

ATT&CK release: 19.2
Object version: 3.0
Created: Jan 23, 2020, 18:53 UTC (UTC+00:00)
Modified: May 12, 2026, 15:12 UTC (UTC+00:00)
Raw hash: 86cab2bf581b9228...

Imported snapshots across ATT&CK releases(2)

Release	Bundle imported	Object version	Modified	Status	Raw hash
19.2	Aug 6, 2026, 02:58 UTC (UTC+00:00)	3.0	May 12, 2026, 15:12 UTC (UTC+00:00)	Current bundle	`86cab2bf581b…`
19.1	Jul 14, 2026, 09:14 UTC (UTC+00:00)	3.0	May 12, 2026, 15:12 UTC (UTC+00:00)	Older bundle	`86cab2bf581b…`

Raw source

Mirrored ATT&CK source object

The raw object is retained through the mirrored ATT&CK source bundle and object hash. The raw endpoint returns the exact object from the mirrored bundle when available.

Open mirrored raw JSON Open MITRE-hosted copy

Source references

External references and citations

MITRE external references are preserved separately from Glexia analysis so citations remain traceable to their original source records.

[1]
Microsoft HTML Help May 2018
Microsoft. (2018, May 30). Microsoft HTML Help 1.4. Retrieved October 3, 2018.
Open source URL
[2]
Microsoft HTML Help ActiveX
Microsoft. (n.d.). HTML Help ActiveX Control Overview. Retrieved October 3, 2018.
Open source URL
[3]
Microsoft HTML Help Executable Program
Microsoft. (n.d.). About the HTML Help Executable Program. Retrieved October 3, 2018.
Open source URL
[4]
MsitPros CHM Aug 2017
Moe, O. (2017, August 13). Bypassing Device guard UMCI using CHM – CVE-2017-8625. Retrieved October 3, 2018.
Open source URL
[5]
Microsoft CVE-2017-8625 Aug 2017
Microsoft. (2017, August 8). CVE-2017-8625 - Internet Explorer Security Feature Bypass Vulnerability. Retrieved October 3, 2018.
Open source URL
[6]
mitre-attackT1218.001
Open source URL

Source and licensing

Source: MITRE ATT&CK®. © 2026 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation. MITRE ATT&CK and ATT&CK are registered trademarks of The MITRE Corporation. Glexia is not affiliated with or endorsed by MITRE.

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