System Binary Proxy Execution: Compiled HTML File

Created the Saturday 04 March 2023. Updated 6 months, 3 weeks ago.

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).

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.

Technique Identifier

T1218.001

Technique Tags

Defense Evasion APT38 APT41 Microsoft HTML Help system hh.exe bypass application application control

Additional Resources

External Links

The resources provided below are associated links that will give you even more detailed information and research on current evasion technique. It is important to note that, while these resources may be helpful, it is important to exercise caution when following external links. As always, be careful when clicking on links from unknown sources, as they may lead to malicious content.

System Binary Proxy Execution: Compiled HTML File, Sub-technique T1218.001 - Enterprise | MITRE ATT&CK®