How does the network police know what a person is doing online at home?

Download a package grabbing software on the Internet, install it on your computer, and grab the data packet of your computer's internet interface, so you can know any information about your interaction with the Internet.

You use the computer to exchange information with the internet, send and receive data packets, which will pass through many nodes (simply speaking, the intersection where the network sends and receives data), so the network police can know "any information" passing through this intersection as long as they catch the data packets (the reason for quoting is that many information in the application layer is encrypted or other security measures are taken, even if these data packets are intercepted, it is not so easy to decrypt the information contained).

However, for your IP address, when did you visit any website, what pictures you saw, what downloads you made, who you chatted with QQ, and so on, the network police and network management can read these basic information whenever they want;

including mobile internet access! !

PS: Mobile Internet access, telephone calls, short messages and multimedia messages can all reveal your location, sometimes even to within a few hundred meters.