type
  PImageImportDescriptor = ^TImageImportDescriptor;
  TImageImportDescriptor = packed record
     HintNameTableOffset: DWORD; // RVA to original unbound IAT, aka Characteristics
                                    // 0 for terminating null import descriptor
                                    // PImageThunkData
     TimeDateStamp : DWORD; // 0 if not bound,
                                    // -1 if bound, and real date\time stamp
                                    // in IMAGE_DIRECTORY_ENTRY_BOUND_IMPORT (new BIND)
                                    // O.W. date/time stamp of DLL bound to (Old BIND)
      ForwarderChain : DWORD; // -1 if no forwarders
      NameOffset : DWORD; // RVA to name of the module we're importing from
      IATOffset : DWORD; // RVA to IAT (if bound this IAT has actual addresses)
                                    // PImageThunkData
  end;

  PImageImportByName = ^TImageImportByName;
  TImageImportByName = packed record
    Hint : WORD;
    Name : array[0..255] of Char;
  end;

  PImageThunkData = ^TImageThunkData;
  TImageThunkData = packed record
    case integer of
      0 : (ForwarderString: PBYTE);
      1 : (FunctionPtr : PDWORD);
      2 : (Ordinal : DWORD);
      3 : (AddressOfData : PImageImportByName);
  end;

procedure PatchIAT(Dll : Pchar; OldFunction : Pointer; newFunc : Pointer);
var
image : LoadedImage;
pImageImportDir : PIMAGEIMPORTDESCRIPTOR;
last : PImageSectionHEader;
size : Cardinal;
dllname : Pchar;
pThunk : PImageThunkData;
lTrue : Boolean;
written : Cardinal;
begin
MapAndLoad(Pchar(ParamStr(0)),nil,@image,True,True);
pImageImportDir := ImageDirectoryEntryToData(
                    image.MappedAddress
                    ,False
                    ,IMAGE_DIRECTORY_ENTRY_IMPORT
                    ,size);

while pImageImportDir.NameOffset <> 0 Do begin
  dllname := ImageRVAToVA(image.FileHeader,image.MappedAddress,pImageImportDir.NameOffset,last);
  If (lstrcmpiA(dllname , Dll) = 0) Then break;
  Inc(pImageImportDir);
end;
{Showmessage(dllname);  }
pThunk := ImageRVAToVA(image.FileHeader,image.MappedAddress,pImageImportDir.IATOffset,last);
While pThunk^.FunctionPtr <> nil Do begin
  Showmessage(FloatTostr(Cardinal(pThunk^.FunctionPtr)));
  Showmessage(IntToStr(Integer(Oldfunction)));
  ltrue := (pThunk^.FunctionPtr = OldFunction );
  If lTrue then begin
    Showmessage('FOUND2');
    {VirtualProtectEx(GetCurrentProcess,pThunk.FunctionPtr,4,PAGE_EXECUTE_READWRITE,written);
    WriteProcessMemory(GetCurrentProcess, pThunk.FunctionPtr, NewFunc, sizeof(NewFunc), Written);
    }break;
  end;
Inc(Pthunk);
end;
UnmapAndLoad(@image);
end;