看起来像服务器被攻击。 /var/log/auth.log的内容如下。 它试图与所有这些用户名ssh，我怎么能closures它。 服务器是Ubuntu。
Feb 22 16:29:15 server sshd[23413]: Failed password for invalid user mirror from 220.132.192.220 port 43881 ssh2 Feb 22 16:29:15 server sshd[23414]: Failed password for invalid user justice from 220.132.192.220 port 43882 ssh2 Feb 22 16:29:15 server sshd[23416]: Failed password for invalid user london from 220.132.192.220 port 43885 ssh2 Feb 22 16:29:15 server sshd[23415]: Failed password for invalid user justice from 220.132.192.220 port 43884 ssh2 Feb 22 16:29:17 server sshd[23421]: Invalid user oxford from 203.66.115.43 Feb 22 16:29:17 server sshd[23421]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:17 server sshd[23421]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=203.66.115.43 Feb 22 16:29:17 server sshd[23422]: Invalid user london from 203.66.115.43 Feb 22 16:29:17 server sshd[23422]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:17 server sshd[23422]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=203.66.115.43 Feb 22 16:29:17 server sshd[23424]: Invalid user london from 203.66.115.43 Feb 22 16:29:17 server sshd[23424]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:17 server sshd[23424]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=203.66.115.43 Feb 22 16:29:17 server sshd[23423]: Invalid user mirror from 203.66.115.43 Feb 22 16:29:17 server sshd[23423]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:17 server sshd[23423]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=203.66.115.43 Feb 22 16:29:19 server sshd[23421]: Failed password for invalid user oxford from 203.66.115.43 port 43959 ssh2 Feb 22 16:29:19 server sshd[23422]: Failed password for invalid user london from 203.66.115.43 port 43962 ssh2 Feb 22 16:29:19 server sshd[23424]: Failed password for invalid user london from 203.66.115.43 port 43967 ssh2 Feb 22 16:29:19 server sshd[23423]: Failed password for invalid user mirror from 203.66.115.43 port 43964 ssh2 Feb 22 16:29:20 server sshd[23429]: Invalid user pacific from 220.132.192.220 Feb 22 16:29:20 server sshd[23429]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:21 server sshd[23429]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=220.132.192.220 Feb 22 16:29:21 server sshd[23430]: Invalid user mirror from 220.132.192.220 Feb 22 16:29:21 server sshd[23430]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:21 server sshd[23430]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=220.132.192.220 Feb 22 16:29:21 server sshd[23432]: Invalid user oxford from 220.132.192.220 Feb 22 16:29:21 server sshd[23431]: Invalid user mirror from 220.132.192.220 Feb 22 16:29:21 server sshd[23432]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:21 server sshd[23432]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=220.132.192.220 Feb 22 16:29:21 server sshd[23431]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:21 server sshd[23431]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=220.132.192.220 Feb 22 16:29:22 server sshd[23429]: Failed password for invalid user pacific from 220.132.192.220 port 44073 ssh2 Feb 22 16:29:22 server sshd[23430]: Failed password for invalid user mirror from 220.132.192.220 port 44078 ssh2 Feb 22 16:29:23 server sshd[23432]: Failed password for invalid user oxford from 220.132.192.220 port 44082 ssh2 Feb 22 16:29:23 server sshd[23431]: Failed password for invalid user mirror from 220.132.192.220 port 44079 ssh2 Feb 22 16:29:24 server sshd[23437]: Invalid user pizza from 202.39.75.16 Feb 22 16:29:24 server sshd[23437]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:24 server sshd[23437]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=202.39.75.16 Feb 22 16:29:24 server sshd[23438]: Invalid user oxford from 202.39.75.16 Feb 22 16:29:24 server sshd[23438]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:24 server sshd[23438]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=202.39.75.16 Feb 22 16:29:24 server sshd[23441]: Invalid user oxford from 202.39.75.16 Feb 22 16:29:24 server sshd[23441]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:24 server sshd[23441]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=202.39.75.16 Feb 22 16:29:24 server sshd[23440]: Invalid user pacific from 202.39.75.16 Feb 22 16:29:24 server sshd[23440]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:24 server sshd[23440]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=202.39.75.16 Feb 22 16:29:26 server sshd[23437]: Failed password for invalid user pizza from 202.39.75.16 port 44173 ssh2 Feb 22 16:29:27 server sshd[23438]: Failed password for invalid user oxford from 202.39.75.16 port 44184 ssh2 Feb 22 16:29:27 server sshd[23441]: Failed password for invalid user oxford from 202.39.75.16 port 44186 ssh2 Feb 22 16:29:27 server sshd[23440]: Failed password for invalid user pacific from 202.39.75.16 port 44185 ssh2 Feb 22 16:29:28 server sshd[23445]: Invalid user quality from 220.132.192.198 Feb 22 16:29:28 server sshd[23445]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:28 server sshd[23445]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=220.132.192.198 Feb 22 16:29:29 server sshd[23446]: Invalid user pacific from 220.132.192.198 Feb 22 16:29:29 server sshd[23446]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:29 server sshd[23446]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=220.132.192.198 Feb 22 16:29:29 server sshd[23448]: Invalid user pacific from 220.132.192.198 Feb 22 16:29:29 server sshd[23448]: pam_unix(sshd:auth): check pass; user unknown Feb 22 16:29:29 server sshd[23448]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=220.132.192.198 Feb 22 16:29:29 server sshd[23450]: Invalid user pizza from 220.132.192.198 Feb 22 16:29:29 server sshd[23450]: pam_unix(sshd:auth): check pass; user unknown 被提了几次我相信：
在Linux Ubuntu上保护SSH
数百个失败的sshlogin
BTW这些尝试是非常普遍的，通常是自动化的脚本。
安装denyhosts 。
apt-get install denyhosts
拒绝主机是一个守护进程，监视你的服务器日志（通常是/var/log/secure ）是否存在可疑的访问模式，如果发现，将好奇的访问者的IP地址添加到/etc/hosts.deny导致sshd直接阻止它们。
它也有一个模式，允许它交换本地阻止列表与其他机器的列表，在某种程度上，众包已知的不良IP地址。 类似于RBL列表为SMTP工作的方式。
我还build议你在你的ssh守护进程上禁用keyboard-interactive身份validation，以防止有人意外创build一个testing用户帐户，并带有一个易于猜测的密码。