Modify ssn connection port ssh port to be 22 by default. We can change it to an unknown port by modifying the configuration file, such as 2222, vim/etc/ssh/sshd-config, open sshd-config with vim editor, and prohibit root users from directly connecting to root through SSH. Everyone knows this account, and it has the highest authority. It is not safe to be directly exposed to the network. We can prohibit ssh from using root connection, and only need to modify ssh configuration file. ah