a computer network that uses the internet but can only be joined by people who have permission or who have the right software

The concept of a darknet is a hidden underground where people anonymously and securely communicate and share files with each other. 暗网这个概念指的是一个隐藏的地下空间，在那里人们可以匿名、安全地交流和共享文件。

Groups can rapidly join and share in a darknet and leave just as easily. 人们可以在暗网中迅速加入小组并共享资源，离开也同样容易。