JavaScript

What the technique is

Adversaries may abuse various implementations of JavaScript for execution. JavaScript (JS) is a platform-independent scripting language (compiled just-in-time at runtime) commonly associated with scripts in webpages, though JS can be executed in runtime environments outside the browser. JScript is the Microsoft implementation of the same scripting standard. JScript is interpreted via the Windows Script engine and thus integrated with many components of Windows such as the Component Object Model and Internet Explorer HTML Application (HTA) pages. JavaScript for Automation (JXA) is a macOS scripting language based on JavaScript, included as part of Apple’s Open Scripting Architecture (OSA), that was introduced in OSX 10.10. Apple’s OSA provides scripting capabilities to control applications, interface with the operating system, and bridge access into the rest of Apple’s internal APIs. As of OSX 10.10, OSA only supports two languages, JXA and AppleScript. Scripts can be executed via the command line utility osascript, they can be compiled into applications or script files via osacompile, and they can be compiled and executed in memory of other programs by leveraging the OSAKit Framework. Adversaries may abuse various implementations of JavaScript to execute various behaviors. […]

What MITRE says you would watch

• AN0733

  Detects JavaScript execution through WSH (wscript.exe, cscript.exe) or HTA (mshta.exe), particularly when spawned from Office macros, web browsers, or abnormal user paths. Correlates script execution with outbound network activity or system modification.

• AN0734

  Detects JavaScript for Automation (JXA) via osascript or compiled scripts using OSAKit APIs. Flags execution involving system modification, inter-process scripting, or browser abuse.

• AN0735

  Detects Node.js or JavaScript interpreter execution from web shells, cron jobs, or local users. Correlates execution with reverse shell behavior, file modifications, or abnormal outbound connections.