Portable Distributed Objects (PDO) is an application programming interface (API) for creating object-oriented code that can be executed remotely on a network of computers. It was created by NeXT Computer, Inc. using their OpenStep system, whose use of Objective-C made the package very easy to write. It was characterized by its very light weight and high speed in comparison to similar systems such as CORBA. The ability to instantiate any object known to the local process from any other process is a known security vulnerability, and Apple strongly discourages use of PDO for that reason.