Bypassing Arxan's integrity checks within Call Of Duty: Black Ops 3

Table of Contents

Introduction #

If you have been modding native game code for Call of Duty: Black Ops 3, you have likely run into its anti-tamper layer, Arxan. This article breaks down an updated integrity check bypass designed specifically for the Black Ops 3 Steam update released in February 2026.

The February 2026 Arxan Recompile #

Previously, developers relied on momo5502's integrity check bypass, which targeted the integrity context earlier in the execution chain. However, the February update shipped with an Arxan recompile that replaced the jmp instructions near several gadgets used in that bypass with stack-obfuscated jmp variants. This change completely broke his split-block signature, rendering the old bypass ineffective.

A New Approach: Targeting the Comparison #

While the previous bypass targeted the integrity context and required significantly more byte patches, this new bypass operates similarly but takes a much simpler path. Instead of fighting the obfuscated stack variables head-on, this bypass targets the locations where the computed checksum and original checksum are actually compared.

By forcing the checksum check to appear correct without modifying the integrity context itself, we can neutralize the protection. Because there are significantly fewer instances of the comparison site compared to the rest of the integrity logic, this becomes the ideal interception point. The simplicity of this bypass allowed it to be condensed to just three lines of code (excluding the signature scanner).

Checksum Comparison Variants #

This bypass works by scanning the game for all instances of the instructions responsible for verifying that the computed checksum of the game's code matches the expected checksum. Three variants of the checksum comparison exist in this version of Arxan. At a high level, each is essentially a variation of the following logic:

                
  cmp computed_checksum, original checksum  // compare the checksums
  jz checksum_matched                       // if the checksums match continue game execution as normal
  jmp crash_game                            // if the checksums do not match, deliberately crash the game
            

By locating these exact comparison points, we can safely overwrite them. The variants are identified by the following byte signatures:

• Variant 1: 8B 0C 8B 33 0C 82
• Variant 2: 8B 0C 8B F7 D9 03 0C 82
• Variant 3 (Unobfuscated Check): 8B 04 82 8B 14 8B 3B C2

Each of these gadgets is replaced with a modified version that forces the comparison to succeed, effectively bypassing the integrity check entirely.

The Bypass Implementation #

The implementation requires a signature scanner to dynamically find and patch these memory locations. Using a custom patch_checksum_comparisons function, we apply the patches like so:

                
  void patch_checksum_comparisons()
  {
    constexpr auto xor_ecx = 0xC933;
    constexpr auto xor_edx = 0xD233;

    // ARXAN XOR table equality check
    // ([rbx + rcx*4] ^ [rdx + rax*4]) == 0
    const auto xor_table_compare = "8B 0C 8B 33 0C 82"_sig;
    for (auto* i : xor_table_compare)
    {
      utils::hook::set(i, xor_ecx);
      utils::hook::nop(i + 2, 4);
    }

    // ARXAN direct table comparison
    // cmp [rdx + rax*4], [rbx + rcx*4]
    const auto cmp_compare = "8B 04 82 8B 14 8B 3B C2"_sig;
    for (auto* i : cmp_compare)
    {
      utils::hook::set(i, xor_ecx);
      utils::hook::set(i + 2, xor_edx);
      utils::hook::nop(i + 4, 4);
    }

    // ARXAN subtraction equality check
    // ([rdx + rax*4] - [rbx + rcx*4]) == 0
    const auto sub_compare = "8B 0C 8B F7 D9 03 0C 82"_sig;
    for (auto* i : sub_compare)
    {
      utils::hook::set(i, xor_ecx);
      utils::hook::nop(i + 2, 6);
    }
  }
                

The underlying scanner safely alters the virtual memory protection, overwrites the target bytes without exceeding the matched signature's length, and flushes the instruction cache:

                
  void copy(void* place, const void* data, const size_t length)
  {
      DWORD old_protect{};
      // Make just the bytes we are going to overwrite RWX.
      VirtualProtect(place, length, PAGE_EXECUTE_READWRITE, &old_protect);

      // Apply the replacement bytes over the first N bytes.
      std::memmove(place, data, length);

      // Restore original protection.
      VirtualProtect(place, length, old_protect, &old_protect);

      // Make sure the CPU sees the modified code.
      FlushInstructionCache(GetCurrentProcess(), place, length);
  }

  void nop(void* place, const size_t length)
  {
      DWORD old_protect{};
      // Make just the bytes we are going to overwrite RWX.
      VirtualProtect(place, length, PAGE_EXECUTE_READWRITE, &old_protect);

      // Apply the NOP bytes (0x90) over the first N bytes.
      std::memset(place, 0x90, length);

      // Restore original protection.
      VirtualProtect(place, length, old_protect, &old_protect);

      // Make sure the CPU sees the modified code.
      FlushInstructionCache(GetCurrentProcess(), place, length);
  }

  template <typename T>
  static void set(void* place, T value = false)
  {
      copy(place, &value, sizeof(value));
  }
                

Important Usage Notes

If you use this implementation in your project, ensure it runs before modifying any bytes in the game. Do not run the patch immediately from a DLL proxy. Wait until the game has finished unpacking its instructions (similar to the timing used in the previous bypass). Otherwise, some comparison gadgets may still be hidden by the packer. Finally, it is unlikely this bypass will work on all older versions of Black Ops 3 since Arxan changes slightly everytime it's used. It is meant purely for the newest version as of March 2026.

Download #

For convenience, you can download the complete source code and implementation in the archive below. Make sure to review the usage notes above before implementing it into your own project.

Summary #

This bypass was originally meant to be private, but community members have recently acquired a less effective integrity check bypass and are now gatekeeping it from people who just want to develop helpful community tools. This bypass was released to ensure community developers have access to a stable, comprehensive, and transparent bypass allowing them the ability to more freely mod the game without any unfair competition.