添加黑名单

找出非法的登录尝试

less /var/log/secure | grep 'Did not receive'

找出频繁的 IP，例如 192.168.11.112，打开 /etc/hosts.deny，添加该 IP：

sshd:192.168.11.112

查看其他

正常登录

less /var/log/secure | grep 'Accepted'

密码有误

less /var/log/secure | grep 'Failed password'