There was such a situation. I run the frida hook on the process like this:

frida -f '..\hack2\hackme.exe'  -l .\start.js

In the script itself I do this

var moduleData = Process.getModuleByName("hackme.exe");

then comes the code which, as a result of which, I launch a function that launches another process - level2.exe.

It would be convenient if you could hook this process directly from this script. calling Process.findModuleByName("level2.exe"); is always null. The only way I see now is to write a Python script that will monitor the launch of the second process and run the hook in different threads. Perhaps there is a simpler solution without resorting to such extreme measures?

  • In difference to a common debugger the Frida JavaScript code is running inside the hooked process, this means you can not simply access a different process. BTW: findModuleByName can only find libraries loaded into the current process, therefore it will never find level2.exe unless it is not started/executed but loaded as library into the current process. I don't see a different way than hooking the seconds process using an external Python script.
    – Robert
    Commented May 1, 2022 at 10:34

1 Answer 1


This is called child-gating and frida has a very good example

Here is a demo with a simple application. A simple C program with a fork and we try to hook puts for both child and parent.

(test3) [frida-example] cat test.c
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
int main() {
  pid_t pid = fork();
  if (pid) {
  } else {
(test3) [frida-example] make test
cc     test.c   -o test

With the example - adding changes

    def _start(self):
        argv = ["./test"]
        print("✔ spawn(argv={})".format(argv))
        pid = self._device.spawn(argv, env={}, stdio='pipe')


    def _instrument(self, pid):
        print("✔ attach(pid={})".format(pid))
        session = self._device.attach(pid)
        session.on("detached", lambda reason: self._reactor.schedule(lambda: self._on_detached(pid, session, reason)))
        print("✔ enable_child_gating()")
        print("✔ create_script()")
        script = session.create_script("""\
Interceptor.attach(Module.getExportByName(null, 'puts'), {
  onEnter: function (args) {
      type: 'puts',
      path: Memory.readUtf8String(args[0])

then by running

(test3) [frida-example] python hook.py
✔ spawn(argv=['./test'])
✔ attach(pid=1968)
✔ resume(pid=1968)
⚡ message: pid=1968, payload={'type': 'puts', 'path': 'before'}
⚡ message: pid=1968, payload={'type': 'puts', 'path': 'parent'}
⚡ child_added: Child(pid=1977, parent_pid=1968, origin=fork)
✔ attach(pid=1977)
✔ resume(pid=1977)
⚡ child_removed: Child(pid=1977, parent_pid=1968, origin=fork)
⚡ message: pid=1977, payload={'type': 'puts', 'path': 'child'}
⚡ detached: pid=1977, reason='process-terminated'

We hooked both the instances of child and parent

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.