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Introduction:
The eternal cat-and-mouse game between security researchers and endpoint detection and response (EDR) systems has entered a new phase with the release of GhostLoad, a Python-based tool that blocks EDR libraries at runtime. This technique represents a significant evolution in offensive security by preventing security DLLs from ever loading into processes, effectively creating blind spots for security monitoring at the user-mode level. Understanding this methodology is crucial for both red teams testing defensive controls and blue teams building more resilient security postures.
Learning Objectives:
- Understand the technical mechanics of runtime DLL blocking and LdrLoadDll hooking
- Implement detection strategies for pre-load interception techniques
- Develop mitigation approaches for EDR library tampering attacks
You Should Know:
1. Understanding the LdrLoadDll Interception Mechanism
Python Script: GhostLoad Core Monitoring Logic
import sys
import ctypes
from ctypes import wintypes
import threading
from debugger import Debugger
Blocklist of security DLLs to intercept
SECURITY_DLL_BLOCKLIST = {
'amsi.dll', 'mpoav.dll', 'mpengine.dll',
'edrdll.dll', 'edrsvc.dll', 'cb.exe'
}
class LdrBlocker:
def <strong>init</strong>(self, target_process):
self.target = target_process
self.debugger = Debugger()
self.hooked = False
def hook_ldrloaddll(self):
Sets hardware breakpoint on LdrLoadDll
ldrloaddll_addr = self.get_ldrloaddll_address()
self.debugger.set_breakpoint(ldrloaddll_addr)
self.hooked = True
Step-by-step guide explaining what this does and how to use it:
This Python code establishes the foundation for intercepting DLL loads by targeting the LdrLoadDll function within ntdll.dll. The SECURITY_DLL_BLOCKLIST contains known EDR and antivirus DLLs that will be blocked from loading. The LdrBlocker class initializes a debugger session and prepares to set breakpoints on the critical loading function. When implemented, this creates a monitoring environment where every DLL load request can be inspected and potentially blocked based on the blocklist.
2. Windows Debugging API Integration for Process Control
C++ Snippet: Debug Object Creation
HANDLE CreateDebuggedProcess(LPCWSTR processPath) {
STARTUPINFOW si = { sizeof(si) };
PROCESS_INFORMATION pi;
if (CreateProcessW(processPath, NULL, NULL, NULL,
FALSE, DEBUG_PROCESS, NULL, NULL, &si, &pi)) {
return pi.hProcess;
}
return NULL;
}
// Debug event loop for monitoring DLL loads
void DebugLoop(HANDLE hProcess) {
DEBUG_EVENT debugEvent;
while (WaitForDebugEvent(&debugEvent, INFINITE)) {
switch (debugEvent.dwDebugEventCode) {
case LOAD_DLL_DEBUG_EVENT:
CheckAndBlockDll(debugEvent.u.LoadDll);
break;
}
ContinueDebugEvent(debugEvent.dwProcessId,
debugEvent.dwThreadId, DBG_CONTINUE);
}
}
Step-by-step guide explaining what this does and how to use it:
This C++ code demonstrates the Windows debugging API integration that GhostLoad utilizes. The CreateDebuggedProcess function launches the target application with DEBUG_PROCESS flag, giving the debugger control over the process. The DebugLoop continuously monitors for debug events, specifically LOAD_DLL_DEBUG_EVENT which triggers whenever a DLL load attempt occurs. This allows the tool to intercept each load request before the DLL is mapped into the process address space.
3. NTDLL Function Hooking Implementation
Assembly Snippet: LdrLoadDll Hook Trampoline ; Hook installation in target process mov rax, [bash] mov [rel original_function], rax ; Install jump to our handler lea rax, [rel our_ldrloaddll_handler] mov [bash], rax ret ; Custom handler logic our_ldrloaddll_handler: push rcx push rdx push r8 push r9 ; Check DLL name against blocklist mov rcx, [rsp+40] ; DLL name parameter call check_blocklist test al, al jnz block_dll ; Allow normal execution pop r9 pop r8 pop rdx pop rcx jmp [rel original_function] block_dll: mov eax, 0xC0000001 ; STATUS_UNSUCCESSFUL add rsp, 32 ret
Step-by-step guide explaining what this does and how to use it:
This assembly code implements the actual hooking mechanism that intercepts LdrLoadDll calls. The trampoline redirects execution to a custom handler that checks the requested DLL name against the blocklist. If the DLL is blocked, the handler returns STATUS_UNSUCCESSFUL, mimicking a failed load. If allowed, execution jumps back to the original LdrLoadDll function. This low-level hook operates before the Windows loader completes its work, making it extremely effective at preventing DLL injection.
4. PowerShell AMSI Bypass Detection and Analysis
PowerShell Commands: Detect AMSI Loading
Check if AMSI is loaded in current PowerShell session
[System.AppDomain]::CurrentDomain.GetAssemblies() |
Where-Object Location -like "amsi" |
Select-Object Location, GlobalAssemblyCache
Monitor DLL loads in real-time
Get-Process -Name powershell |
ForEach-Object {
$_.Modules |
Where-Object ModuleName -like "amsi" |
Select-Object ProcessName, ModuleName, FileName
}
Windows Event Log analysis for AMSI bypass
Get-WinEvent -FilterHashtable @{
LogName='Microsoft-Windows-PowerShell/Operational'
Id=4104
} | Where-Object Message -like "amsi"
Step-by-step guide explaining what this does and how to use it:
These PowerShell commands help blue teams detect whether AMSI is properly loaded or has been blocked by tools like GhostLoad. The first command checks currently loaded assemblies for AMSI components, the second monitors active PowerShell processes for AMSI modules, and the third queries Windows event logs for AMSI-related activity. Regular monitoring of these indicators can help identify successful EDR bypass attempts in enterprise environments.
5. EDR Telemetry Gap Identification
KQL Query: Detect Missing Security DLLs
SecurityEvent
| where EventID == 4688 // Process creation
| where NewProcessName contains "powershell.exe"
| where CommandLine contains "-nop -w hidden"
| extend ProcessId = tostring(NewProcessId)
| join kind=leftouter (
DeviceImageLoadEvents
| where FileName in ("amsi.dll", "mpoav.dll", "edrdll.dll")
| where Timestamp > ago(5m)
) on ProcessId
| where isnull(FileName) // Missing expected security DLLs
| project TimeGenerated, Computer, NewProcessName,
CommandLine, ProcessId
Step-by-step guide explaining what this does and how to use it:
This Kusto Query Language (KQL) query helps security analysts identify processes that should have security DLLs loaded but don’t—a key indicator of successful GhostLoad-style attacks. The query joins process creation events with image load events, looking for PowerShell processes that lack expected security DLLs. Implementing this type of detection across your SIEM can help identify compromised systems where EDR visibility has been degraded.
6. Memory Forensics for Hook Detection
Volatility Framework Commands: Scan for inline hooks in ntdll.dll volatility -f memory.dump --profile=Win10x64_18362 apihooks volatility -f memory.dump --profile=Win10x64_18362 ssdt Check for debug objects and abnormal process relationships volatility -f memory.dump --profile=Win10x64_18362 handles -t DebugObject volatility -f memory.dump --profile=Win10x64_18362 pslist volatility -f memory.dump --profile=Win10x64_18362 psscan Detect DLLs loaded from unusual locations volatility -f memory.dump --profile=Win10x64_18362 ldrmodules volatility -f memory.dump --profile=Win10x64_18362 malfind
Step-by-step guide explaining what this does and how to use it:
These Volatility commands enable forensic investigators to detect evidence of LdrLoadDll hooking after the fact. The apihooks plugin identifies function hooks, handles detects debug objects that shouldn’t be present in normal processes, and ldrmodules/malfind help identify DLLs loaded from unexpected locations or injected code. Regular memory analysis can uncover sophisticated attacks that evade traditional disk-based detection.
7. Kernel-Level Protections Against User-Mode Hooking
Windows Security Configuration: Enable Windows Defender Attack Surface Reduction rules Set-MpPreference -AttackSurfaceReductionRules_Ids \ D1E49AAC-8F56-4280-B9BA-993A6D77406C \ -AttackSurfaceReductionRules_Actions Enabled Configure Windows Defender Exploit Guard New-CIPolicy -FilePath BlockDllHooks.xml -Level SignedAndReputable ConvertFrom-CIPolicy -XmlFilePath BlockDllHooks.xml \ -BinaryFilePath BlockDllHooks.bin Deploy via Group Policy or MDM Enable Protected Processes Light (PPL) for critical services reg add "HKLM\SYSTEM\CurrentControlSet\Control\Srp\GP" \ /v "DllBlockPolicy" /t REG_BINARY /d BlockDllHooks.bin
Step-by-step guide explaining what this does and how to use it:
These Windows security configurations help mitigate user-mode hooking attacks by implementing kernel-level protections. The Attack Surface Reduction rules prevent Office applications from creating child processes, Exploit Guard policies can block untrusted DLLs, and Protected Processes Light (PPL) adds additional security to critical services. Deploying these configurations enterprise-wide significantly raises the bar for attackers attempting EDR bypass techniques.
What Undercode Say:
- The shift from post-execution hook evasion to pre-load DLL blocking represents a fundamental change in offensive security tradecraft
- Current EDR architectures relying on user-mode injection are inherently vulnerable to these techniques
- Organizations must implement defense-in-depth with kernel-level protections and behavioral monitoring
The GhostLoad technique exposes critical architectural weaknesses in modern EDR solutions that predominantly rely on user-mode hooking for visibility. While the immediate impact enables red teams to operate more effectively, the broader implication is that security vendors must accelerate their transition to kernel-mode and hardware-assisted monitoring approaches. The cybersecurity industry’s over-reliance on user-space interception has created a systemic vulnerability that sophisticated threat actors will inevitably exploit. Defenders must immediately augment their detection capabilities with network traffic analysis, kernel-level telemetry, and behavioral analytics that don’t depend on user-mode DLL injection for visibility.
Prediction:
Within the next 18-24 months, GhostLoad-style techniques will become standardized in advanced attack frameworks, forcing a fundamental architectural shift in endpoint security. EDR vendors will be compelled to migrate significant monitoring capabilities to the kernel level or risk irrelevance against sophisticated adversaries. This evolution will trigger increased adoption of hardware-assisted security features like Intel CET and Microsoft Pluton, while simultaneously driving regulatory scrutiny of endpoint security products. The resulting arms race will permanently alter the endpoint security landscape, potentially creating new vulnerability classes at the kernel level while rendering current user-mode hooking paradigms obsolete.
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IT/Security Reporter URL:
Reported By: Deepanshukhanna Ghostloadblocking – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
