What is the fifth space? How to defend the fifth space in China?

As we know, land, ocean, sky and outer space constitute a four-dimensional space, and now the Internet provides great convenience for people's food, clothing, housing and transportation, and is called the fifth space.

However, due to the virtual, transnational and technical concealment of the fifth space, it has also brought shocks to national security, privacy and property. So crack down on hackers, guard and maintain network security, and defend the fifth space of our great motherland.