I found NACL64.EXE was in my wordpress server. It's located in wp-content/uploads/2012/08. But I don't think I uploaded it. I did google but confused with results, for example: http://www.prevx.com says "You should urgently check your PC to make sure it is not infected." 2. other said: nacl64.exe is a Google Chrome process which belongs to Google Chrome from Google Inc.
Is it a kind of virus please?