ntdlldll

ntdll.dll, short for NT Layer Dynamic Link Library, is a core Windows system library that provides the Windows NT native API and serves as a bridge between user-mode processes and the kernel. It is a dynamic link library loaded into nearly every Windows process and is essential for basic system operation.

The module exports a large set of functions, many with Nt or Rtl prefixes, used to perform low-level operations such as creating processes, opening files, querying system information, memory management, and exception handling. It also contains components for the loader (such as LdrLoadDll) and the RTL runtime. Because it exposes a native API leveraged by higher-level libraries, it plays a central role in how Windows implements its services.

Location and versioning: Ntdll.dll is located in the Windows System32 directory (C:\Windows\System32 on 64-bit Windows, with a separate copy in SysWOW64 for 32-bit processes on 64-bit systems). It is updated with Windows releases and is compiled for the system’s architecture.

System role: The file is loaded at process startup and is used by many higher-level DLLs to implement Windows APIs. The surface area exposed by ntdll.dll encompasses the Native NT API, which underpins portions of the Win32 API implemented in other system DLLs such as kernel32.dll and ntdll’s own components.

Security and stability: Because it is essential to the kernel-interface, corruption or tampering with ntdll.dll can cause crashes or system instability. The file is protected by Windows integrity mechanisms and is a frequent target in malware attacks, underscoring its critical role in system reliability.