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 as VBA, JScript, Java, and ActiveX.1 CHM content is displayed using underlying components of the Internet Explorer browser2 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 control on older and/or unpatched systems that do not account for execution of binaries through hh.exe.45
- Microsoft HTML Help May 2018
- Microsoft HTML Help ActiveX
- Microsoft HTML Help Executable Program
- MsitPros CHM Aug 2017
- Microsoft CVE-2017-8625 Aug 2017
Groups using this technique
| Group | Name | Country |
|---|---|---|
| grp_g0070 | Dark Caracal | — |
| grp_g0049 | OilRig | Iran |
| grp_g0082 | APT38 | DPRK |
| grp_g0091 | Silence | — |
| grp_g0096 | APT41 | China |
Claims
No public claim points at this technique yet.
Auto-ingested and not human-reviewed; confidence and validity read by citation.