Mobile devices have become the de facto standard for communication. Almost all adults in first world countries use one or more mobile devices for work, entertainment, and communication. This means that there are many more devices on a given network and the Internet as a whole, further establishing the fact that there are many more opportunities for hackers to gain access to personal and private information. Mobile devices come with their own ways of protecting personal resources. Describe at least four different types of network security defenses that mobile operating systems provide in order to keep personal data safeguarded. Also, answer the question of who is ultimately responsible for securing personal data: the operating system vendor, or those who own the device hosting the operating system?