Process enumeration is a technique used by malware to identify and analyze running processes in a system and in this article we are going to see an alternative one.
It’s a critical step for malware that aims to inject its code into legitimate processes, thereby avoiding detection.
This technique allows malware to blend with normal system operations, making it difficult for security software and analysts to identify the threat.
Malware developers often employ different enumeration methods as a way to camouflage their malicious code.
However, cybersecurity experts are aware of this tactic and look for signs of such activities. Knowing this, malware developers are constantly seeking new and more sophisticated methods of process enumeration to stay ahead of security measures.
The concept of alternative process enumeration is not entirely new, but it evolves with advancements in malware technology. I found a nice approach to this method in a micro paper from VX Underground. It represents a refined way for malware to perform process enumeration, making it even more challenging for analysts to detect.
For malware analysts, understanding these methods is crucial. It helps them develop better strategies and tools to identify and counteract such tactics. So the message of the article is that as malware analysts, we need to stay informed about the latest developments in malware techniques.
Understanding Process Enumeration in Malware Analysis
Process enumeration in malware refers to a method where the malware scans and identifies active processes on a host system. This technique serves two primary purposes:
- First, it helps the malware find a suitable process to inject its malicious code into. This is crucial for the malware to integrate seamlessly into the system without being easily detected (you can see how enumeration is used in our dedicated articles: DLL Injection and Process Injection).
- Second, it assists the malware in determining an environment that allows it to operate undetected. Here, the malware assesses the system to find the most conducive conditions for its survival and functioning. For example, it can try to check for the presence of a debugger software.
At its heart, process enumeration is about being stealthy and efficient. Malware developers design their programs to carry out this task in a way that’s both unnoticeable and uses minimal resources. This stealth is achieved through the malware querying the operating system for a list of running processes, and then selecting the most suitable ones for code injection. The selection is based on criteria such as the process’s privileges, its stability, and the extent of monitoring by security software.
The knowledge of each variant enables malware analysts to devise more effective strategies for detecting and neutralizing threats. By identifying the patterns and techniques used in process enumeration, they can pinpoint potential vulnerabilities and fortify their systems against such intrusions.
Furthermore, this understanding is instrumental in developing advanced security protocols and tools. These tools are designed to closely monitor process behaviours, detecting anomalies that could indicate attempts at process enumeration. Staying ahead in recognizing these tactics equips malware analysts to better protect systems and data against cyber threats.
The EnumWindows and EnumDesktopWindows API
- EnumWindows: API is designed to enumerate all top-level windows on the screen. This function works by passing every top-level window handle to an application-defined callback function. This is particularly useful for malware that needs to identify active applications, gather window titles for potential target processes, or even find a specific application’s window to carry out UI-based attacks.
- EnumDesktopWindows is more specific in its scope. This API enumerates all top-level windows associated with a particular desktop – typically the one that is currently active. It’s crucial for malware that targets specific user environments or applications running within a particular desktop context. For example, if malware is designed to operate or inject code in a corporate environment, it could be used
EnumDesktopWindowsto identify and target applications commonly used in such settings.
From a malware analyst’s perspective, monitoring the usage of these APIs can be a key indicator of suspicious activity. Malware may use these functions to scout for potential injection targets or gather information about the user’s environment. Thus, security tools and analysts often keep a close watch on the invocation of these APIs, as their misuse can be a red flag indicating potential malicious activity. By understanding how EnumWindows and EnumDesktopWindows are utilized, malware analysts can better anticipate and mitigate tactics employed by malware, enhancing overall system security.
The EnumWindowsProcesses Callback
Both the functions we presented need a callback as an argument: EnumWindowsProc.
The EnumWindowsProc callback function is a crucial component when working with the EnumWindows or EnumDesktopWindows functions. It acts as a direct inspector of each top-level window presented by these APIs.
Let’s break down its structure and purpose. As the documentation suggests, this is the syntax:
BOOL CALLBACK EnumWindowsProc(
_In_ HWND hwnd,
_In_ LPARAM lParam
);- The
hwndparameter here is a handle for each top-level window that the function evaluates. It’s the unique identifier for windows in the system. - The
lParamparameter, on the other hand, is an application-defined value. It’s used by the function for additional context or information as needed during the window examination process.
The function’s return value is straightforward yet critical.
- If
EnumWindowsProcreturnsTRUE, it indicates the continuation of the enumeration process, signalling the function to keep inspecting further windows. - If it returns
FALSE, the enumeration stops. This could either mean that the function has found a window of interest or that it has completed its task.
Before this function can be put to use, it needs to be registered. This registration process involves passing the function’s address to either EnumWindows or EnumDesktopWindows. This step is essential for the function to operate within the Windows environment.
In essence, EnumWindowsProc serves as a functional tool within Windows programming, enabling developers to specify how each top-level window should be processed. Whether for identifying potential process injection targets or other application-specific purposes, this function provides a structured and efficient way to examine windows in the operating system.
Delineating Differences: Micropaper vs. Article Approach
The original micro paper and our expanded article exhibit key differences in approach, particularly in the context of ‘alternative process injection’. Primarily, the micropaper utilizes the GetProcessImageFilenameW function within its code. This function needs parsing to compare with a target process name and extract only the filename, a crucial step for identifying a specific process. In contrast, our article shifts the focus to spotting a particular process more directly.
Furthermore, the original micropaper doesn’t detail how to obtain the process handle from the callback function. Our article aims to bridge this gap. It will illustrate how to effectively use the lParam parameter within the callback function. This involves passing the name of the process and storing the handle for later retrieval in the main body of the code.
This added explanation is vital for understanding the complete mechanism of process enumeration and handle retrieval, offering a more comprehensive guide to those delving into the intricacies of alternative process injection techniques.
The Callback: Exploring the Core Function
In this part of our discussion on ‘alternative process injection’, we’re diving into the heart of the callback function, specifically how it identifies and returns the handle to a desired process. The function, EnumWindowsProc, is defined as follows:
BOOL CALLBACK EnumWindowsProc(IN HWND hwnd, IN LPARAM lParam ) {
DWORD dwPID;
TCHAR wcName[MAX_NAME_SIZE];
HMODULE hModule;
DWORD dwCbNeeded;
ProcessInfo* targetProcessInfo = (ProcessInfo*)(lParam);
if(GetWindowThreadProcessId(hwnd, &dwPID))
{
HANDLE hProcess = OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ, FALSE, dwPID);
if (hProcess != NULL)
{
if (EnumProcessModules(hProcess, &hModule, sizeof(hModule), &dwCbNeeded))
{
GetModuleBaseName(hProcess, hModule, wcName, sizeof(wcName)/sizeof(TCHAR));
if(_tcsicmp(wcName, targetProcessInfo->target) == 0)
{
targetProcessInfo->hProcess = hProcess;
return FALSE;
}
}
else {
CloseHandle(hProcess);
}
}
else {
_tprintf(_T("Error in OpenProcess: %d\n"), GetLastError());
}
return TRUE;
}
else
{
return FALSE;
}
}Inside this function, our primary goal is to locate a specific process and then capture its handle. We start by defining variables like dwPID for the process ID, wcName for the process name, and hModule, which will be used in the module enumeration.
The real action begins with GetWindowThreadProcessId. This function retrieves the process ID associated with the window handle hwnd. If this succeeds, we proceed to open the process for query and reading. This is where OpenProcess comes into play.
Once we have access to the process, EnumProcessModules helps us get the first module of the process, essentially giving us a snapshot of the process’s executable. We then use GetModuleBaseName to get the name of this module (or the process).
The critical comparison happens next. We check if the retrieved process name matches our target process, defined in targetProcessInfo->target. If it’s a match, we store the process handle in targetProcessInfo->hProcess and return FALSE to stop the enumeration.
If we don’t find a match, or if there’s an error in opening the process (for example we cannot open processes that are running with higher privileges than our program), we continue the enumeration by returning TRUE. This makes the function keep looking through other windows until it finds the target process or runs out of windows to check.
In essence, this callback function is a systematic way to iterate through processes, pinpoint the desired one, and retrieve its handle, which is a critical step in the process of alternative process injection.
The Main: Setting the Stage for Process Enumeration
Now, let’s walk through the main function, which sets the stage for our exploration of ‘alternative process injection’. The main function in our code looks like this:
int main()
{
ProcessInfo targetProcessInfo = { NULL, _T("notepad.exe") };
_tprintf(_T("Initial process handle: %p, process name: %ws\n"), targetProcessInfo.hProcess, targetProcessInfo.target);
EnumWindows(EnumWindowsProc, (LPARAM)&targetProcessInfo);
if (targetProcessInfo.hProcess != NULL) {
_tprintf(_T("Found process handle: %p, process name: %ws\n"), targetProcessInfo.hProcess, targetProcessInfo.target);
CloseHandle(targetProcessInfo.hProcess); // Close the handle when done
}
else {
_tprintf(_T("Process not found\n"));
}
return 0;
}Here’s what’s happening in simple terms. First, we create a ProcessInfo structure named targetProcessInfo. This structure is crucial as it holds the handle (initially NULL) and the name of the process we’re looking for, in this case, notepad.exe.
We then print the initial state of targetProcessInfo, showing that at this point, we don’t have a handle for our target process yet.
The critical function call here is EnumWindows(EnumWindowsProc, (LPARAM)&targetProcessInfo);. This line is where we invoke the enumeration of windows. We pass in our EnumWindowsProc function and a pointer to targetProcessInfo as arguments. Essentially, we’re starting our search for the notepad.exe process among all the top-level windows.
After EnumWindows completes its run, we check if targetProcessInfo.hProcess is no longer NULL. If it’s not, it means we successfully found our target process, and we print the obtained process handle. This is a key moment, as it confirms the successful identification and handling of the target process.
Finally, if we find the process, we responsibly close the handle using CloseHandle(targetProcessInfo.hProcess). It’s important to close handles when we’re done with them to avoid resource leaks. If we didn’t find the process, we simply printed a message stating that the process was not found.
In conclusion, the main function in this scenario is responsible for initiating the process enumeration and handling the outcome, whether that’s successfully finding the target process or not finding it. This function essentially sets the entire process enumeration operation in motion.
Conclusion
So far, we have explored the process enumeration in Windows programming, particularly focusing on the EnumWindowsProc callback function within the EnumWindows API. We’ve demonstrated how this function navigates through each top-level window to identify a specific process returning its handle.
By dissecting the callback and main functions, we unveil tools from the attacker’s arsenal, enabling you as a defender to anticipate and counter malicious tactics effectively.
Understanding these mechanisms is vital for anyone in cybersecurity, whether enhancing security protocols, developing robust software, or simply staying ahead in the tech game.
We hope this article has expanded your understanding of malware developers’ minds.
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