CreateRemoteThread

Description

Used to start a thread in a remote process (one other than the calling process). Launchers and stealth malware use CreateRemoteThread to inject code into a different process.

Use the CreateRemoteThreadEx function to create a thread that runs in the virtual address space of another process and optionally specify extended attributes.

Syntax

HANDLE WINAPI CreateRemoteThread(
  _In_   HANDLE hProcess,
  _In_   LPSECURITY_ATTRIBUTES lpThreadAttributes,
  _In_   SIZE_T dwStackSize,
  _In_   LPTHREAD_START_ROUTINE lpStartAddress,
  _In_   LPVOID lpParameter,
  _In_   DWORD dwCreationFlags,
  _Out_  LPDWORD lpThreadId
);

Parameters

hProcess [in]

A handle to the process in which the thread is to be created. The handle must have the PROCESS_CREATE_THREAD, PROCESS_QUERY_INFORMATION, PROCESS_VM_OPERATION, PROCESS_VM_WRITE, and PROCESS_VM_READ access rights, and may fail without these rights on certain platforms.

lpThreadAttributes [in]

A pointer to a SECURITY_ATTRIBUTES structure that specifies a security descriptor for the new thread and determines whether child processes can inherit the returned handle. If lpThreadAttributes is NULL, the thread gets a default security descriptor and the handle cannot be inherited. The access control lists (ACL) in the default security descriptor for a thread come from the primary token of the creator.

Windows XP: The ACLs in the default security descriptor for a thread come from the primary or impersonation token of the creator. This behavior changed with Windows XP with SP2 and Windows Server 2003.

dwStackSize [in]

The initial size of the stack, in bytes. The system rounds this value to the nearest page. If this parameter is 0 (zero), the new thread uses the default size for the executable. For more information, see Thread Stack Size.

lpStartAddress [in]

A pointer to the application-defined function of type LPTHREAD_START_ROUTINE to be executed by the thread and represents the starting address of the thread in the remote process. The function must exist in the remote process. For more information, see ThreadProc.

lpParameter [in]

A pointer to a variable to be passed to the thread function.

dwCreationFlags [in]

The flags that control the creation of the thread.

Value	Meaning
0	The thread runs immediately after creation.
CREATE_SUSPENDED 0x00000004	The thread is created in a suspended state, and does not run until the ResumeThread function is called.
STACK_SIZE_PARAM_IS_A_RESERVATION 0x00010000	The dwStackSize parameter specifies the initial reserve size of the stack. If this flag is not specified, dwStackSize specifies the commit size.

lpThreadId [out]

A pointer to a variable that receives the thread identifier.

If this parameter is NULL, the thread identifier is not returned.

Return value

If the function succeeds, the return value is a handle to the new thread.

If the function fails, the return value is NULL. To get extended error information, call GetLastError.

Note that CreateRemoteThread may succeed even if lpStartAddress points to data, code, or is not accessible. If the start address is invalid when the thread runs, an exception occurs, and the thread terminates. Thread termination due to a invalid start address is handled as an error exit for the thread's process. This behavior is similar to the asynchronous nature of CreateProcess, where the process is created even if it refers to invalid or missing dynamic-link libraries (DLL).

DLL

• Kernel32.dll