1.修改端口号，设置登录输入密码等待过期时间，拒绝远程登录root，密码为空，密码登录，

[root@zzp124 ~]# vim /etc/ssh/sshd_config       

[root@zzp124 ~]# systemctl restart sshd.service 
[root@zzp124 ~]# lsof -i :22
[root@zzp124 ~]# lsof -i :66
COMMAND  PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
sshd    3476 root    3u  IPv4  39248      0t0  TCP *:sql*net (LISTEN)
sshd    3476 root    4u  IPv6  39250      0t0  TCP *:sql*net (LISTEN)

2.设置开机自启

systemctl enable sshd    设置开机自启

3.计算机私人密钥文件

[root@zzp124 ~]# head -3 /etc/ssh/ssh_host_rsa_key
-----BEGIN RSA PRIVATE KEY-----
MIIEowIBAAKCAQEAo3lCTvgoQXzO55VtFM5KhL6ylvfF8LIAldml144G7pnDm7oX
Myt55ScUbvZLKv6nYVkBnD+JqXhUyvZB/zUzKUA8hUMdq/48brRjXY0wwRgerfyM

4.登录日志存放文件

[root@zzp124 ~]# head -3 /var/log/secure 
Nov  9 00:00:21 localhost polkitd[700]: Loading rules from directory /etc/polkit-1/rules.d
Nov  9 00:00:21 localhost polkitd[700]: Loading rules from directory /usr/share/polkit-1/rules.d
Nov  9 00:00:22 localhost polkitd[700]: Finished loading, compiling and executing 8 rules

5.设置登录提示

6.控制外界服务器IP是否可以访问本机

[root@zzp124 ~]# vim /etc/hosts.allow 			#设置允许访问的IP，优先级高于deny

[root@zzp124 ~]# vim /etc/hosts.deny 				#设置拒绝访问的IP