Z3rodumper

Executables in memory are laid out with sections aligned to page boundaries (usually 0x1000). When saved to disk, sections must be aligned to file alignment (typically 0x200). z3rodumper recalculates raw offsets and fixes the PE headers to produce a runnable or analyzable file.

To appreciate Z3roDumper, one must understand the "dump" in its name. Dumping is not as simple as reading a process’s memory and saving it to a file. Obfuscated .NET binaries often employ anti-dump techniques, such as:

Z3roDumper uses a combination of the following techniques to counter this:

| Protection Technique | Description | Bypass Method | |----------------------|-------------|----------------| | NtReadVirtualMemory hook | Protector hooks the API to return garbage data | Kernel-mode direct read | | PAGE_NOACCESS on sections | Makes sections unreadable to cause crash | Temporarily change page protection via ZwProtectVirtualMemory (from kernel) | | Stolen bytes | Original code moved to encrypted heap | Pattern match and relocate | | Anti-debug timers | Checks for time drift indicating breakpoints | Patch timer functions in memory | | TLS callbacks | Run code before entry point to detect dumping | Suspend process before TLS execution | z3rodumper

Many dumpers simply copy the raw memory as-is, resulting in a corrupted PE file. Z3roDumper attempts to reconstruct the original section table. It identifies the .text section (where the IL code lives) and the metadata streams (#~, #Strings, #US, #GUID, #Blob) to ensure that the dumped file can be re-opened in a decompiler like dnSpy or ILSpy.

Based on reverse engineering of similar dumpers (including public leaks and forum discussions), z3rodumper likely incorporates the following techniques:

If you want to understand the internals without using questionable tools, here’s a safe, educational approach using Microsoft’s Detours library and the WinAPI: Executables in memory are laid out with sections

// Simplified memory dumper skeleton
#include <windows.h>
#include <dbghelp.h>
BOOL DumpProcess(DWORD pid, const char* outPath)  PROCESS_VM_READ, FALSE, pid);
if (!hProcess) return FALSE;
// Enumerate modules
HMODULE hMods[1024];
DWORD cbNeeded;
EnumProcessModules(hProcess, hMods, sizeof(hMods), &cbNeeded);
for (int i = 0; i < (cbNeeded / sizeof(HMODULE)); i++) 
    MODULEINFO modInfo;
    GetModuleInformation(hProcess, hMods[i], &modInfo, sizeof(modInfo));
// Allocate buffer and read memory
    BYTE* buffer = (BYTE*)malloc(modInfo.SizeOfImage);
    if (ReadProcessMemory(hProcess, modInfo.lpBaseOfDll, buffer, modInfo.SizeOfImage, NULL)) 
        // Fix headers, rebuild IAT, write to file
free(buffer);
CloseHandle(hProcess);
return TRUE;

This basic dumper will work for unprotected processes. To turn it into something like z3rodumper, you would need to implement kernel-mode reading, VAD walking, and anti-anti-debug tricks.

Companies sometimes lose the source code for legacy line-of-business applications that are obfuscated for distribution. If the application still runs, Z3roDumper can recover a close-to-original version, allowing maintenance or migration to new platforms.