Frida

Frida is a dynamic instrumentation toolkit that lets developers and security researchers inject custom JavaScript into running processes across platforms (Windows, macOS, Linux, iOS, Android) for debugging, profiling, and reverse-engineering.

Frida is primarily a dynamic analysis tool, as it injects instrumentation code into live processes to observe and manipulate their behavior at runtime.

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Frida is a “live” instrumentation framework that lets me attach to a running process, hook into its functions, and inject my own code (written in JavaScript or Python), all without needing the original binaries’ source or rebooting the system.

In other words, it behaves very much like a debugger—but one where I can dynamically redefine or intercept any function in a process at runtime.

Why Frida is handy on macOS?

No source-code needed

I don’t have to rebuild or recompile a kernel extension, daemon, or GUI app to see what internal routines are doing.

Frida injects a small runtime library (the “agent”) into the target process and exposes every exported symbol (and even non-exported code addresses) via a JS API.

Real-time hooking

Once attached, I can write a short snippet in JavaScript like:

  Interceptor.attach(Module.getExportByName(null, "open"), {
    onEnter(args) {
      console.log("open() called with:", args[0].readUtf8String());
    }
  });

That snippet will print every path passed to open(…) by the process as it happens—no restart required.

Modify behavior on the fly

I can observe arguments and return values, and mutate them. For instance, I could intercept a system call that checks for a security entitlement and force it to always return “success,” or override the return value of mach_msg in a kernel extension to see what happens.

Bypass symbol-stripping and lack of debug information

Even if an Apple-supplied daemon is stripped down or I don’t have its dSYM, Frida can still locate function boundaries (by pattern or by walking the Mach-O headers) and let me interpose on any address.

In short, Frida functions as a debugger for live processes on macOS in real time and without needing to rebuild or reboot.