# Skill Endpoint Detection And Response

> Skill Endpoint Detection And Response

- Skill: `thedixitjain/skill-endpoint-detection-and-response` (Agent Skill)
- Install (CLI): `npx skillmds add thedixitjain/skill-endpoint-detection-and-response`
- Raw SKILL.md: https://api.skillmd.com/api/skills/thedixitjain/skill-endpoint-detection-and-response/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- Author: thedixitjain (https://skillmd.com/u/thedixitjain)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/thedixitjain/skill-endpoint-detection-and-response

---

# SKILL: Endpoint Detection and Response

## Metadata
- **Skill Name**: edr-evasion
- **Folder**: offensive-edr-evasion
- **Source**: https://github.com/SnailSploit/offensive-checklist/blob/main/edr.md

## Description
EDR evasion offensive checklist: hook unhooking (user/kernel), direct syscalls, PPID spoofing, process injection variants, AMSI bypass, ETW patching, memory encryption, and behavior-based evasion. Use when planning EDR bypass during red team engagements or researching AV/EDR evasion techniques.

## Trigger Phrases
Use this skill when the conversation involves any of:
`EDR evasion, EDR bypass, hook unhooking, direct syscalls, PPID spoofing, process injection, AMSI bypass, ETW patch, memory encryption, AV evasion, behavioral evasion, red team evasion`

## Instructions for Claude

When this skill is active:
1. Load and apply the full methodology below as your operational checklist
2. Follow steps in order unless the user specifies otherwise
3. For each technique, consider applicability to the current target/context
4. Track which checklist items have been completed
5. Suggest next steps based on findings

---

## Full Methodology

# Endpoint Detection and Response

## Fundamentals

### AV vs EDR

**Antivirus (preventive approach)**:

- Static Analysis: Matching known signatures in files
- Dynamic Analysis: Limited behavioral monitoring/sandboxing
- Effective against known threats, weaker against advanced attacks

**EDR (proactive & investigative approach)**:

- Continuous endpoint monitoring
- Behavioral analysis at kernel level
- Anomaly detection and post-compromise visibility
- Prioritizes incident response and investigation

### Windows Execution Flow

Windows program execution follows a hierarchical flow:

1. **Applications** - User programs like firefox.exe
2. **DLLs** - Libraries providing Windows functionality without direct low-level access
3. **Kernel32.dll** - Core DLL for memory management, process/thread creation
4. **Ntdll.dll** - Lowest user-mode DLL that exposes the NT API interface to the kernel
5. **Kernel** - Core OS component with unrestricted hardware access

Example operation flow (creating a file):

1. Application invokes `CreateFile` function
2. CreateFile forwards to `NtCreateFile`
3. Ntdll.dll triggers `NtCreateFile` syscall
4. Kernel creates the file and returns a handle

## EDR Visibility

### EDR Architecture & Components

EDR solutions consist of multiple components creating a complex attack surface:

**Client-Side Components:**

- **User-space Applications** - Main agent processes and UI components
- **Kernel-space Drivers** - Filter drivers, network drivers, software drivers
- **Communication Interfaces** - IOCTLs, FilterConnectionPorts, ALPC, Named Pipes

**Component Communication Methods:**

- **Kernel-to-Kernel**: Exported functions, IOCTLs
- **User-to-Kernel**: IOCTLs, FilterConnectionPorts (minifilter-specific), ALPC
- **User-to-User**: ALPC, Named Pipes, Files, Registry

**Server-Side Components:**

- Cloud services and management consoles
- On-premise servers (some vendors)
- Custom protocols for agent-to-cloud communication

### EDR Visibility Methods

EDR solutions require extended visibility into system activities:

- Filesystem monitoring via mini-filter drivers
- Process/module loading via image load kernel callbacks
- Process/.NET modules/Registry/kernel object events via ETW Ti
- Network monitoring via NDIS and network filtering drivers

### Static Analysis

- Extract information from binary
  - Known malicious strings
  - Threat actor IP or domains
  - Malware binary hashes

### Dynamic Analysis

- Execute binary in a sandbox environment and observe it
  - Network connections
  - Registry changes
  - Memory access
  - File creation/deletion
- AntiMalware Scan Interface

### Behavioral Analysis

- Observe the binary as its executing, Hook into functions/syscalls
  - User actions
  - System calls
  - Kernel callbacks
  - Commands executed in the command line
  - Which process is executing the code
  - Event Tracing for Windows

## Detection Methods

### AV Signature Scanning

- Scans files using known signatures (YARA rules)
- Typically targets loaders and droppers
- Primarily static analysis of files on disk

### AV Emulation

- Runs suspicious programs in a simulated environment
- Triggers on behaviors without executing real code
- Used to detect obfuscated malware

### Usermode Hooks

- EDR hooks critical API calls in userspace (ntdll.dll)
- Monitors process creation, memory allocations, and network operations
- Allows for inspection before execution continues

### Kernel Telemetry

- Monitors events directly from the kernel
- Captures file, registry, process, and network operations
- Difficult to bypass as it operates at a lower level

### Memory Scanning

- Scans process memory for known signatures
- Triggers based on suspicious behavior
- Looks for shellcode, encryption, malicious strings
- **Modern Context:**
  - Attackers also scan process memory for sensitive artifacts like authentication tokens. Co‑pilot/IDE integrations, chat assistants, and browser extensions frequently cache Bearer/JWT tokens in memory.
  - Practical triage: search for `"Authorization: Bearer"`, `"eyJ"` (base64 JWT prefix), or provider‑specific headers; dump minimal pages to avoid tripping anti‑exfil rules.

## OpSec Quickstart (lab)

- Pre‑run
  - Network: block or sinkhole vendor EDR/XDR endpoints; disable cloud sample submission; tag lab hosts.
  - Mitigations snapshot: `Get-ProcessMitigation -System`; `Get-CimInstance Win32_DeviceGuard` (VBS/HVCI/KDP); `Get-MpPreference` (ASR/Cloud).
  - Events baseline: enable and tail `Microsoft-Windows-CodeIntegrity/Operational`, `Security (4688/4689)`, `Microsoft-Windows-Sense/Operational`, Sysmon (if present).
- Injection hygiene
  - Favor `MEM_IMAGE` mappings (ghosting/herpaderping/overwriting) over `MEM_PRIVATE` RWX to avoid 24H2 hotpatch loader checks.
  - Satisfy XFG/CET: jump via import thunks; ensure IBT `ENDBR64` at indirect targets; maintain plausible stacks for syscalls (replicate `ntdll` frames).
  - Avoid noisy APIs: split `alloc/write/exec` over time; prefer APC+`NtContinue` pivots; keep thread contexts consistent.
- Telemetry minimization
  - Jitter long‑lived channels; prefer named‑pipe/HTTP3 over noisy HTTP1; throttle upload intervals.
  - Use COM/runspace over PowerShell console to reduce script‑block logs; avoid AMSI‑flagged prologues.
- Cleanup
  - Remove services, tasks, drivers; restore SDDL; revert registry policy flips (WDAC/CI/Defender) and re‑enable protections.
  - Purge user caches (Recent Files, Jump Lists) and ETW providers enabled during tests.

### Memory Regions

- Monitors suspicious memory allocation patterns
- Flags RWX (read-write-execute) regions
- Tracks regions that change from RW to RX

### Callstack Analysis

- Examines the call stack of suspicious functions
- Verifies legitimate origin of critical operations
- Detects unusual function call chains

### Hook Implementation

EDRs can't directly hook kernel memory due to PatchGuard, so they:

1. Inject their DLL into newly spawned processes
2. Position before malware can block/unmap it
3. Adjust `_PEB`, hook process's module `IAT`/Imports, and loaded libraries `EAT`/Exports
4. Implement trampolines, hooks, and detours

### ETW Monitoring

- EDR maintains ring-buffer with per-process activities produced by ETW Ti:
  - Processes, command lines, parent-child relationships
  - File/Registry/Process open/write operations
  - Created threads, their call stacks, starting addresses
  - Native functions called
  - Created .NET AppDomains, loaded .NET assemblies, static class names, methods

#### Event Correlation

- High fidelity alert (such as LSASS open) triggers correlation of collected activities
- High memory/resources cost limits preservation of events to a time window
- ML/AI may compute risk scores and isolate TTP (Tactics, Techniques, and Procedures)

#### Shellcode Loaders

Shellcode loaders typically follow this pattern:

```c
char *shellcode = "\xAA\xBB...";
char *dest = VirtualAlloc(NULL, 0x1234, 0x3000, PAGE_READWRITE);
memcpy(dest, shellcode, 0x1234)
VirtualProtect(dest, 0x1234, PAGE_EXECUTE_READ, &result)
(*(void(*)())(dest))();  // jump to dest: execute shellcode
```

## Attacking EDR Infrastructure Directly

### Driver Attack Surface Analysis

A systematic approach to analyzing EDR drivers from a low-privileged user perspective:

#### 1. Driver Discovery

**Static Analysis:**

```powershell
# List loaded drivers
driverquery /v
Get-WindowsDriver -Online -All

# Using WMI
Get-WmiObject Win32_PnPSignedDriver | Select-String "EDR_Vendor"
```

**Dynamic Analysis:**

```powershell
# Using sc command
sc query type= driver state= all

# Process Monitor filtering
# Filter: Process and Thread Activity -> Show Image/DLL
```

#### 2. Interface Enumeration

**Device Driver Interfaces:**

- Listed in WinObj under "GLOBAL??" as Symbolic Links
- Accessible via `\\.\DEVICE_NAME` format
- Tools: WinObj (Sysinternals), DeviceTree (OSR - discontinued)

**Mini-Filter Driver Interfaces:**

- Listed in WinObj as "FilterConnectionPort" objects
- Communication via `FltCreateCommunicationPort` API
- Example paths: `\CyvrFsfd`, `\SophosPortName`

#### 3. Access Permission Analysis

**Device Driver ACL Checking:**

```cpp
// Using DeviceTree (preferred) or kernel debugger
// WinDbg example:
!object \Device\DeviceName
!sd <SecurityDescriptor_Address> 1
```

**FilterConnectionPort ACL Checking:**

```powershell
# Using NtObjectManager (James Forshaw)
Get-FilterConnectionPort -Path "\FilterPortName"
# Error indicates access denied

# In WinDbg:
!object \FilterPortName
dx (((nt!_OBJECT_HEADER*)0xAddress)->SecurityDescriptor & ~0xa)
!sd <SecurityDescriptor_Address> 1
```

#### 4. Interface Functionality Analysis

**Device Driver Communication:**

- Primary method: DeviceIoControl() → IRP_MJ_DEVICE_CONTROL
- IOCTL codes differentiate between functions
- May include process ID verification for authorization

**FilterConnectionPort Communication:**

- Uses callback functions: ConnectNotifyCallback, DisconnectNotifyCallback, MessageNotifyCallback
- Similar to IOCTL dispatch with different message types

#### 5. Common EDR Driver Interfaces

**Examples of accessible interfaces found in research:**

**Palo Alto Cortex XDR:**

- **Device Interfaces**:
  - `\\.\PaloEdrControlDevice` (tedrdrv.sys) - ~20 IOCTL handlers with various functionality
  - `\\.\CyvrMit` (cyvrmtgn.sys) - Legacy Cyvera interface
  - `\\.\PANWEdrPersistentDevice11343` (tedrpers-<version>.sys) - Persistent device interface
- **FilterConnectionPort**: Various ports with different ACLs
- **Research Findings**:
  - IOCTL 0x2260D8 returns 3088 bytes of statistics data (accessible to low-privileged users)
  - IOCTL 0x2260D0 provides initialization status information
  - Some interfaces accessible due to injected DLL architecture requiring broad permissions

**Sophos Intercept X:**

- **FilterConnectionPort**: `\SophosPortName`
- **Analysis Results**: Accessible interfaces for legitimate process communication but limited attack surface

#### 6. Why EDRs Have Open ACLs

EDRs often use an architecture where:

- Agent injects DLLs into processes (including low-privileged ones like `word.exe`)
- Injected DLLs communicate directly with drivers via IOCTLs
- Drivers cannot restrict based solely on process privilege level
- Results in more permissive ACLs to accommodate legitimate injected processes

## Evasion Techniques

### Memory-Based Evasion

#### EDR-Freeze

A novel technique exploiting Windows Error Reporting (WER) to temporarily disable EDR/AV processes:

##### Mechanism

- Leverages `WerFault.exe` and Windows Error Reporting infrastructure
- Suspends all threads in target EDR/AV processes indefinitely
- No kernel-mode access or driver exploitation required
- Operates entirely from user-mode context

##### Technical Implementation

- Trigger WER fault injection on target security process
- WER suspends all threads for crash dump generation
- Attacker maintains suspended state without completing crash handling
- Target process remains alive but non-functional

##### Advantages

- No elevation required in default WER configurations
- Avoids detection heuristics for process termination
- Temporary disabling without unloading kernel drivers
- Minimal forensic footprint compared to driver killing

##### Limitations

- Effectiveness varies by Windows version and WER configuration
- Some EDRs implement anti-suspension protections
- Temporary nature requires continuous re-application
- May generate WER event logs exposing the technique

> [!TIP]
> Blue team detection: Alert on `PssSuspendProcess` / `PssSuspendThread` API calls combined with `OpenProcess` targeting EDR process IDs, or monitor Event ID 1001 (Windows Error Reporting) with unusual source processes.

#### Memory Encryption

- Encrypts shellcode in memory when not in use
- Popular techniques:
  - SWAPPALA / SLE(A)PING
  - Thread Pool / Pool Party
  - Gargoyle
  - Ekko
  - Cronos
  - Foliage

#### Sleep Obfuscation

- ROP-Styles sleep obfuscations
  - [Ekko](https://github.com/Cracked5pider/Ekko)
  - [FOLIAGE](https://github.com/y11en/FOLIAGE)
  - these setup `_CONTEXT` in advance so that `EIP/RIP` points to native API
  - and then schedule APC with `NtContinue` to jump to that requested API

#### Secure Enclaves (VBS)

- Virtualization-Based Security (VBS) enclaves provide an isolated user-mode TEE that even kernel-mode sensors cannot inspect under normal conditions.
- Deprecation/support scope (Microsoft):
  - Windows 11 ≤ 23H2: VBS enclaves are deprecated; existing enclaves signed with the legacy EKU (OID `1.3.6.1.4.1.311.76.57.1.15`) continue to run until re-signed. New enclave signing requires updated EKUs and is not supported on these versions.
  - Windows 11 24H2+ and Windows Server 2025: VBS enclaves are supported with new EKUs.
- Security fix: CVE-2024-49076 (VBS Enclave EoP) — ensure December 2024+ updates are applied.
- Signing constraints: Only Microsoft-signed enclave DLLs or DLLs signed via Azure Trusted Signing load; test- or self-signed DLLs are rejected.
- Architecture summary:
  - Enclave host app (VTL0) invokes enclave APIs; enclave DLL executes in isolated user mode (VTL1) with restricted API surface; Secure Kernel validates integrity.
- Offensive considerations (lab): viable for secure storage of secrets/implants during sleep and for hiding sensitive code paths; limited by restricted API surface and signing requirements.
- Practical notes:
  - On unsupported SKUs/versions, enclave APIs may appear and return `STATUS_FEATURE_DEPRECATED`.
  - Prefer testing on Windows 11 24H2+/Server 2025 with proper signing.

#### Malware Virtualization

- Malware virtualization provides advanced evasion against modern EDR:
  - Embeds a custom virtual machine to execute bytecode instead of native code
  - Makes static and dynamic analysis difficult through instruction obfuscation
  - Prevents detection of instruction patterns and behavior prediction

- Implementation advantages:
  - Conceals malicious instructions from EDR monitoring
  - Protects against code patching attempts
  - Hinders behavioral analysis through custom execution model

- Multi-VM approach further evades detection:
  - Multiple VMs running concurrently disrupts heuristic pattern detection
  - Each VM creates distinct event patterns, confusing EDR correlation
  - "ETW noise" technique to blend with legitimate activity

- Deployment strategies:
  - Bytecode polling - periodically fetching new instructions from C2
  - Using transpilers to convert compiled binaries to custom bytecode
  - Applying polymorphic engine to mutate VM code itself

- Successfully evaded detection for:
  - Initial shellcode/bytecode execution (subsequent actions still monitored)
  - Specific AV/EDR patching routines (may require updates per product)
  - Initial C2 communication (ongoing traffic patterns may be detected)
  - Specific AD queries (patterns of queries can still be flagged)

### QEMU-Based Virtualization Evasion

- **Concept**: Deploy portable QEMU VMs to execute malicious code within guest OS, avoiding host-based EDR detection
- **Technical Implementation**:
  - Portable QEMU deployment via ZIP archives containing VM binaries and configurations
  - Tiny Core Linux as lightweight guest OS (minimal footprint ~50MB)
  - VBS scripts for automated VM deployment and execution
  - Custom hostname generation for VM identification and tracking

- **Configuration Examples**:

  ```vbs
  # VBS deployment script
  Set shell = CreateObject("WScript.Shell")
  shell.Run "tc.exe -m 512 -hda tc.qcow2 -netdev user,id=net0 -device e1000,netdev=net0"
  ```

  ```conf
  # QEMU configuration file (upd.conf)
  -m 512
  -hda tc.qcow2
  -netdev user,id=net0
  -device e1000,netdev=net0
  ```

- **Persistence Mechanisms**:
  - `bootlocal.sh` modifications for startup execution
  - `filetool.lst` configuration for file persistence across reboots
  - SSH service installation and configuration within guest VM
  - Reverse SSH tunnels over port 443 for C2 communication

- **Advanced Techniques**:
  - Anti-forensic SSH configuration (`StrictHostKeyChecking=no`, known hosts to `/dev/null`)
  - SSL/NoSSL tool deployment for encrypted communications
  - Randomized hostname generation to mask VM tracking
  - Port 443 tunneling to blend with HTTPS traffic

- **Detection Evasion Benefits**:
  - Guest VM operations invisible to host-based EDR sensors
  - VM network traffic appears as legitimate application activity
  - File operations contained within guest filesystem
  - Process execution isolated from host monitoring

- **Limitations & Considerations**:
  - Requires administrative privileges for some QEMU operations
  - VM resource consumption may be detectable
  - Network traffic patterns might still trigger detection
  - Initial VM deployment artifacts remain on host filesystem

### Hook Evasion

#### Unhooking

- malware overwrites EDR hooks before executing payload
- you can obtain original `ntdll.dll` from disk and overwrite it inside your own process
- or you can start the malware process in suspended state and copy the clean `ntdll.dll` from you own memory before executing
  - **Modern Context:** While historically effective, relying solely on replacing `ntdll.dll` or its hooked sections is less reliable. Modern EDRs often use kernel callbacks, ETW, and other telemetry sources that are not bypassed by user-mode unhooking alone. This technique is often used in conjunction with others.
    > [!CAUTION]
    > accessing `ntdll.dll` file can be flagged, API call to overwrite it also might be hooked by EDR

##### API Unhooking for AV Bypass

- Most EDR/AVs like BitDefender hook Windows APIs by replacing first bytes with `JMP` instructions (opcode `0xE9`)
- **Modern Context:** Similar to general unhooking, patching specific API prologues can bypass simple user-mode hooks, but comprehensive EDR solutions have additional detection layers (kernel events, behavioral analysis) that may still detect the malicious activity following the unhook.
- How to identify hooked APIs:
  - Create a test program that calls potentially hooked APIs
  - Examine first byte of API function using a debugger (like x64dbg)
  - If first byte is `0xE9`, the function is hooked
- Common hooked APIs:
  - `CreateRemoteThread`/`CreateRemoteThreadEx`
  - `VirtualAllocEx`
  - `WriteProcessMemory`
  - `OpenProcess`
  - `RtlCreateUserThread`
- Unhooking approach:
  1. Store original bytes of target APIs from clean system
  2. Identify hooked functions in memory
  3. Restore original bytes using `WriteProcessMemory` on the current process
  4. Execute malicious code using now-unhooked APIs
- Sample implementation:

  ```c
  // Find address of target API function
  HANDLE kernelbase_handle = GetModuleHandle("kernel32");
  LPVOID CreateRemoteThread_address = GetProcAddress(kernelbase_handle, "CreateRemoteThread");

  // Check if function is hooked (first byte is 0xE9)
  byte first_byte = (byte)*(char*)CreateRemoteThread_address;
  if (first_byte == 0xe9) {
      // Replace with original bytes
      char original_bytes[] = "\x4C\x8B\xDC\x48\x83"; // Original prologue bytes
      WriteProcessMemory(GetCurrentProcess(), CreateRemoteThread_address, original_bytes, 5, NULL);
  }
  ```

- This technique is effective but may require separate execution for the final payload since some AVs block executing immediately after unhooking. **Modern EDRs might still correlate the unhooking activity with subsequent suspicious actions.**

#### Unhooking Tools

- [unhook BOF](https://github.com/rsmudge/unhook-bof) - module refreshing (less reliable now **due to alternative EDR telemetry sources**)
- [Unhookme](https://github.com/mgeeky/UnhookMe) - dynamic unhooking

#### Direct System Calls

- malware circumvents hook in system DLL by directly system calling into kernel
- you can implement own syscall in assembly and bypass `ntdll.dll` hooks
- or obtain `SSN`(System Service Number) dynamically and call them(can be done via [SysWhispers2](https://github.com/jthuraisamy/SysWhispers2))
  - Direct syscalls bypass user-mode hooks in `ntdll.dll` but do not inherently bypass kernel-level monitoring (e.g., via kernel callbacks or ETW). EDRs are increasingly monitoring for patterns indicative of direct syscall usage itself (e.g., unusual call stack origins for syscalls).
    > [!CAUTION]
    > having syscall assembly instructions can be flagged, also this only helps the loader to evade the EDR not the malware itself
  - Major EDR vendorsnow flag **non‑ntdll syscall sites**; consider **return‑address replication gadgets** to re‑insert a plausible `ntdll` frame before the transition.

> [!CAUTION]
> Some EDRs flag syscalls originating outside `ntdll.dll`. Maintaining plausible stacks/return frames may be required to avoid heuristics.

##### Direct Syscall Tools

Bypasses user-mode hooks but not kernel monitoring. Requires System Service Dispatch Table (SSDT) index:

- [FreshyCalls](https://github.com/crummie5/FreshyCalls) - sorting system call addresses
- [SysWhispers2](https://github.com/jthuraisamy/SysWhispers2) - modernized syscall resolution
- [SysWhispers3](https://github.com/klezVirus/SysWhispers3) - adds x86/Wow64 support
- [Runtime Function Table](https://www.mdsec.co.uk/2022/04/resolving-system-service-numbers-using-the-exception-directory/) - reliable SSN computation

#### Indirect System Calls

- malware uses code fragments in kernel DLL without calling the hooked functions in those DLL
- prepare the system call in assembly then find a syscall instruction in `ntdll.dll` and jump to that location
  - **Modern Context:** Similar to direct syscalls, this bypasses user-mode hooks but not necessarily kernel-level monitoring. Finding and jumping to existing `syscall` instructions can be less suspicious than embedding raw syscall stubs, but the subsequent kernel activity is still visible.
    > [!TIP]
    > this is preferred,you can also boost evasion techniques by hiding inside a `.dll`

#### Kernel‑Mode EDR Killers (BYOVD)

- **Bring‑Your‑Own‑Vulnerable‑Driver (BYOVD)** attacks load legitimately signed but exploitable drivers—examples include **rtcore64.sys**, **iqvw64e.sys**, and **terminator.sys**—to execute privileged code inside the kernel.
- Typical payload actions
  - Patch or unregister kernel‑mode notify callbacks (`PsSetCreateProcessNotifyRoutine`, `ObRegisterCallbacks`) to blind user‑mode EDR components.
  - Overwrite or unload _WdFilter.sys_ and other sensor drivers, fully disabling Defender or third‑party agents.
- Public toolchains such as **Terminator**, **kdmapper**, and **EDRSensorDisabler** automate these steps.
- Case study: Lenovo `LnvMSRIO.sys` (CVE‑2025‑8061). Exposes physical memory/MSR read‑write primitives to low‑privileged users; can overwrite MSR_LSTAR and pivot to Ring‑0 payload, then patch/unregister callbacks to blind EDR.

> [!TIP]
> The vulnerable‑driver blocklist (`DriverSiPolicy.p7b`) is **enabled by default** on Windows 11 22H2+ and refreshed every Patch Tuesday. Keep HVCI/KDP enabled so attacker drivers cannot patch protected code pages, and enable Hardware‑Enforced Stack Protection (CET/Shadow Stack) on Windows 11 24H2 to break call‑stack spoofing.

> [!NOTE]
> Because the blocklist is on by default and updated frequently, a BYOVD chain now often needs **two** vulnerable drivers: one to disable Secure Boot or flip `CiOptions`, and a second to perform the EDR‑killer actions before the next blocklist refresh.

### User-Mode Application Whitelisting Bypass

#### Exploiting Vulnerable Trusted Applications

Windows Defender Application Control (WDAC) and similar application whitelisting solutions can be bypassed by leveraging vulnerabilities in trusted, signed applications. A notable technique involves exploiting N-day vulnerabilities in the V8 JavaScript engine within Electron-based applications.

- **Concept (Bring Your Own Vulnerable Application - BYOVA)**:
  - A trusted, signed Electron application (e.g., an older version of VSCode) with a known V8 vulnerability is used as a carrier.
  - The application's `main.js` (or equivalent) is replaced with a V8 exploit that executes a native shellcode payload.
  - If the application is whitelisted, WDAC allows it to run, inadvertently executing the malicious shellcode.
- **Advantages**:
  - Achieves native shellcode execution, overcoming limitations of pure JavaScript execution in some backdoored Electron app scenarios.
  - Shellcode runs in a browser-like process context, where behaviors like Read-Write-Execute (RWX) memory regions (due to JIT compilers) are common and may appear less suspicious to EDRs.
- **Exploit Development & Operationalization Challenges**:
  - **V8 Version Targeting**: Electron's V8 often lags behind Chrome's and includes backported security patches. Vulnerabilities must be chosen that were patched _after_ the target application's Electron version was frozen. Electron's cherry-picked patches should be reviewed.
  - **Debugging**: Building the specific V8 version (e.g., using `d8` debug shell with `--allow-natives-syntax` for `%DebugPrint()`) is crucial for understanding memory layouts and adapting exploits.
  - **Offset Inconsistencies**: Hardcoded offsets in public exploits (often Linux-based) need adjustment for the target V8 version and OS (Windows). Function pointer offsets for overwriting can even vary between Windows versions.
    - _Solution for offset variation_: Launch the exploit multiple times in child processes, each trying a different potential offset. The parent process monitors for success (e.g., mutex creation by payload).
  - **Sandbox Escape**: Public V8 exploits might use sandbox escape techniques already patched (cherry-picked) in the target Electron V8 version, requiring new or modified escapes.
  - **JIT Compiler Interference (e.g., V8 TurboFan)**:
    - Optimizations can consolidate repeated instruction sequences (e.g., multiple floating-point values), affecting shellcode smuggling. Workarounds include compact shellcode or varying instruction positions.
    - Copying large shellcode payloads can be problematic. Workaround: multiple smaller copy loops or using a stager payload that fetches the main payload.
  - **Payload Obfuscation**: Obfuscate the JavaScript exploit (e.g., in `main.js`) to hinder analysis. Re-obfuscating per deployment can help avoid signature-based detection.
- **Defense & Future Considerations**:
  - Electron's experimental integrity fuse feature, if enabled by developers, can verify the integrity of application files (including `main.js`) at runtime, potentially thwarting this technique by exiting if tampering is detected.
  - Older application versions without this fuse remain vulnerable.

### Process Manipulation

#### Early Cascade Injection

- Novel process injection technique targeting user-mode process creation
- Combines elements of Early Bird APC with EDR-Preloading
- Avoids queuing cross-process APCs while maintaining minimal remote process interaction
- Works by:
  - Targeting processes during the transition from kernel-mode to user-mode (`LdrInitializeThunk`)
  - Leveraging callback pointers (like `g_pfnSE_DllLoaded`) during Windows process creation
  - Executing malicious code before EDR detection measures can initialize
- Advantages:
  - Operates before EDRs can initialize their hooks and detection measures
  - Particularly effective against EDRs that hook `NtContinue` or use delayed initialization
  - Avoids ETW telemetry that traditional injection techniques trigger
  - Minimal remote process interaction reduces detection footprint
  - More stealthy than traditional techniques like DLL hijacking or direct syscalls
- Key insight: EDRs typically load their detection measures after the `LdrInitializeThunk` function executes, providing a window of opportunity for code execution before security measures initialize
- watch for early `NtCreateThreadEx` inside `LdrInitializeThunk`

#### Early Startup Bypass

**Concept**: Execute malware before the EDR's user-mode component fully initializes, creating a window of opportunity for undetected execution.

**Implementation**:

- Target the gap between kernel driver loading and user-mode agent initialization
- Execute payload during system startup before EDR hooks are established
- Leverage services that start before EDR components

**Research Findings (Cortex XDR)**:

- Successfully executed Mimikatz with `lsadump::sam` without detection during early startup
- EDR kernel drivers may be loaded but user-mode hooks not yet established
- Timing window varies depending on system performance and EDR implementation

**Detection Evasion**:

- Creates process activity before EDR monitoring is fully operational
- Avoids user-mode hooks that haven't been established yet
- Kernel-level monitoring may still detect activity depending on driver initialization order

**Limitations**:

- Requires precise timing and understanding of EDR startup sequence
- May not work against EDRs with early kernel-level monitoring
- Window of opportunity may be brief on fast systems

#### Waiting Thread Hijacking (WTH)

- A stealthier version of classic Thread Execution Hijacking
- Intercepts the flow of a waiting thread and misuses it for executing malicious code
- Avoids suspicious APIs like `SuspendThread`/`ResumeThread` and `SetThreadContext` that trigger most alerts
- Required handle access:
  - For target process: `PROCESS_VM_OPERATION`, `PROCESS_VM_READ`, `PROCESS_VM_WRITE`
  - For target thread: `THREAD_GET_CONTEXT`
- Uses less monitored APIs:
  - `NtQuerySystemInformation` (with `SystemProcessInformation`)
  - `GetThreadContext`
  - `ReadProcessMemory`
  - `VirtualAllocEx`
  - `WriteProcessMemory`
  - `VirtualProtectEx`
- Implementation can be further obfuscated by splitting steps across multiple functions to evade behavioral signatures
- Primarily bypasses EDRs that focus on detecting specific API calls rather than behavioral patterns
- Effective against EDRs that are restrictive about remote execution methods but more lenient with allocations and writes
- Suitable for hiding the point at which implanted code was executed

#### PPID Spoofing

- Creates process with fake parent process ID
- Hides true process creation chain
- Makes process tree analysis misleading

#### Process Hiding

A technique to hide processes from EDR monitoring by manipulating the Interrupt Request Level (IRQL):

- Raise the IRQL of current CPU core
- Create and queue Deferred Procedure Calls (DPCs) to raise the IRQL of other cores
- Perform sensitive task (for example, hiding process)
- Signal DPCs in other cores to stop spinning and exit
- Lower IRQL of current core back to original

```c
irql = RaiseIRQL();
dpcPtr = AcquireLock();
do_stuff();
ReleaseLock(dpcPtr);
LowerIRQL(irql);
```

This approach temporarily prevents EDR from monitoring the process during the critical operations by operating at an elevated privilege level.

> [!NOTE]
> HVCI-enabled 23H2 kernels may crash when raising IRQL this way. Safer alternative: kernel-driver patching of `PsLookupProcessByProcessId`.

#### UAC Bypass via Intel ShaderCache Directory

- Concept: Exploits weak permissions (`Authenticated Users: Full Control`) on the `Intel\ShaderCache` directory (`%LOCALAPPDATA%\LocalLow\Intel\ShaderCache`) combined with the behavior of auto-elevated processes (like `taskmgr.exe`) writing to this location.
- Mechanism:
  1.  Clear Directory: Requires aggressively terminating processes holding handles (`explorer.exe`, `sihost.exe`, etc.) and deleting files within the `ShaderCache` directory. Permissions might need adjustment (`icacls`) to allow deletion. Launching `taskmgr.exe` briefly (with a timeout) helps identify recently written filenames and can trigger writes needed for the exploit.
  2.  Junction Creation: Create a directory junction from `ShaderCache` to `\??\GLOBALROOT\RPC CONTROL`.
  3.  Symbolic Link: Determine a recently used filename within `ShaderCache` (before clearing). Create an object directory symbolic link (`CreateDosDevice`) from `Global\GLOBALROOT\RPC CONTROL\<recent_filename>` to a target DLL path (e.g., `\??\C:\Windows\System32\oci.dll`).
  4.  Trigger Write: Launch an auto-elevated process (e.g., `taskmgr.exe`) that writes to `ShaderCache`. The write operation follows the junction and then the symbolic link, resulting in the creation of a (dummy) target file (e.g., `oci.dll`) in a privileged location (`System32`).
  5.  Overwrite & Execute: Overwrite the created dummy file with the actual malicious DLL. Launch a process (like `comexp.msc`) that attempts to load the target DLL, thereby executing the malicious code with elevated privileges.
- EDR Relevance:
  - Bypasses User Account Control (UAC), a primary defense layer.
  - Relies on manipulating file system objects (junctions, symlinks) and process interactions that EDRs monitor.
  - Involves potentially noisy actions like mass process termination and permission changes.
  - The final payload execution often relies on DLL hijacking techniques.

> [!TIP]
> Symlink/junction UAC races are build‑dependent and brittle. Validate on the specific target build; many have partial or complete mitigations.

#### PPL (Protected Process Light) Bypass

**Concept**: Bypass Protected Process Light security by creating alternative service configurations that avoid PPL protections.

**Palo Alto Cortex XDR PPL Bypass Technique**:

```powershell
# Create alternative service that launches cyserver.exe without PPL protection
sc create "fake_cyserver" binPath="C:\Program Files\Palo Alto Networks\Traps\cyserver.exe" start=auto
```

**How it works**:

- Creates a second service that launches the EDR's main process (cyserver.exe)
- Original PPL-protected service fails to start due to startup dependencies
- New service configuration is not protected by EDR drivers
- EDR process runs without PPL protection, expanding attack surface

**Limitations**:

- Service names beginning with "cyserver\*" are blocked by some EDR implementations
- EDR functionality may remain intact despite PPL bypass
- Self-protection mechanisms may still be active at process level
- Vendor response varies - may not be considered a security vulnerability

**Detection & Response**:

- EDR thinks original service is stopped but agent continues running
- Attack surface increases as process no longer has PPL protections
- Reported to Palo Alto on 12.09.2023 with limited vendor response

**Broader Implications**:

- Demonstrates service configuration vulnerabilities in EDR implementations
- Shows potential for bypassing Windows security features through alternative execution paths
- Relevant for other EDRs that rely on PPL for self-protection

#### Using `NtCreateUserProcess` for Stealthy Process Creation

The native API `NtCreateUserProcess()`, located in `ntdll.dll`, is the lowest-level user-mode function for creating processes. Calling it directly can bypass EDR hooks placed on higher-level functions like `CreateProcessW` in `kernel32.dll`. This makes it a valuable technique for stealthier process creation.

**Key Concepts:**

- **Bypass Mechanism**: Avoids user-land hooks on more commonly monitored APIs like `CreateProcessW`.
- **Process Parameters**: Requires careful setup of structures like `RTL_USER_PROCESS_PARAMETERS` (often via `RtlCreateProcessParametersEx`), `PS_CREATE_INFO`, and `PS_ATTRIBUTE_LIST`.
  - `RTL_USER_PROCESS_PARAMETERS`: Defines process startup information, including image path, command line, environment variables, etc. The `ImagePathName` must be in NT path format (e.g., `\??\C:\Windows\System32\executable.exe`).
  - `PS_ATTRIBUTE_LIST`: Can specify attributes like the image name.
- **Flags**: `ProcessFlags` and `ThreadFlags` allow fine-grained control over process and thread creation (e.g., creating suspended). Sources like Process Hacker's headers (`ntpsapi.h`) can provide valid flag definitions. For minimal use, these can sometimes be `NULL`.
- **Implementation Details**: Involves initializing several structures and using functions from `ntdll.dll` such as `RtlInitUnicodeString`, `RtlCreateProcessParametersEx`, and `RtlAllocateHeap`. The article also mentions that the `ProcessParameters` argument for `NtCreateUserProcess` was found to be mandatory, and `RtlCreateProcessParametersEx` is used with the `RTL_USER_PROCESS_PARAMETERS_NORMALIZED` flag. The `PS_CREATE_INFO` structure needs its `Size` and `State` (e.g., `PsCreateInitialState`) members initialized. The `PS_ATTRIBUTE_LIST` is populated to include the image name.

**Example High-Level Steps:**

1.  Define the path to the executable using `UNICODE_STRING` and initialize it with `RtlInitUnicodeString` (e.g., `L"\??\C:\Windows\System32\calc.exe"`).
2.  Create and populate `RTL_USER_PROCESS_PARAMETERS` using `RtlCreateProcessParametersEx`, providing the image path and normalizing parameters.
3.  Initialize a `PS_CREATE_INFO` structure.
4.  Allocate and initialize a `PS_ATTRIBUTE_LIST`, setting the `PS_ATTRIBUTE_IMAGE_NAME` attribute with the image path.
5.  Call `NtCreateUserProcess` with the prepared handles, access masks, and structures.
6.  Perform cleanup, for instance, by calling `RtlFreeHeap` and `RtlDestroyProcessParameters`.

This technique allows for creating a new process with more direct control, potentially evading EDRs that primarily hook `kernel32.dll` API calls. However, EDRs with kernel telemetry or hooks deeper within `ntdll.dll` (or monitoring syscalls directly) might still detect the `NtCreateUserProcess` call or the subsequent behavior of the spawned process.

#### Advanced Process Execution Alternatives

- [TangledWinExec](https://github.com/daem0nc0re/TangledWinExec) - alternative process execution techniques
- [rad9800](https://github.com/rad9800/misc/blob/main/bypasses/WorkItemLoadLibrary.c) - indirectly loading DLL through a work item

#### Acquiring Process Handles

- Without using suspicious `OpenProcess`:
  - Find `explorer.exe` window handle using `EnumWindows`
  - Convert to process handle with `GetProcessHandleFromHwnd`
  - Leverage `PROCESS_DUP_HANDLE` to duplicate into a pseudo handle for [Full Access](https://jsecurity101.medium.com/bypassing-access-mask-auditing-strategies-480fb641c158)

### Callstack Manipulation

#### Return Address Overwrite

- overwrite function's return address with 0
  - that terminates call stack's unwinding algorithm
  - examination based on `DbgHelp!StackWalk64` fails
- implement custom API resolver similar to `GetProcAddress`
  - before calling out to suspicious functions, overwrite `RetAddr :=0`
  - when system API returns, restore own `RetAddr`

#### Callstack Spoofing

- Manipulates the call stack to appear legitimate
- Makes it harder to detect malicious code execution
- Tools and techniques:
  - ThreadStackSpoofer
  - CallStackSpoofer
  - AceL

…(truncated)