说明：
在查询限制服务器被SSH尝试时，有看到一个说，可以修改/etc/ssh/sshd_config配置文件的MaxAuthTries参数。但这个参数其实是限制SSH客户端一次连接服务器，能测试的密码的。找了个说明，具体如下
Specifies the maximum number of authentication attempts permitted per connection. Once the number of failures reaches half this value, additional failures are logged. The default is 6.
实现：
MaxAuthTries要生效，必须修改SSH服务端、客户端
1. 修改SSH服务端
# vim /etc/ssh/sshd_config #MaxAuthTries 6 //系统默认是6次。可以按需要更改，如改为2或其它。注意删除#，并重启sshd使配置生效
2. 修改SSH客户端
# ssh -o NumberOfPasswordPrompts=8 carl@192.168.2.200 //通过-o NumberOfPasswordPrompts指定1次连接可以尝试的密码，默认是3次。即1次连接可以输入3次密码。但这个就没办法试出MaxAuthTries 6这个的效用了 carl@192.168.2.200's password: Permission denied, please try again. carl@192.168.2.200's password: Permission denied, please try again. carl@192.168.2.200's password: Permission denied, please try again. carl@192.168.2.200's password: Permission denied, please try again. carl@192.168.2.200's password: Permission denied, please try again. carl@192.168.2.200's password: Received disconnect from 192.168.2.200: 2: Too many authentication failures for carl
可以看到尝试6次系统就断开连接了。如果需要尝试次数更少的，可以修改第1步的MaxAuthTries，改为2或其它。
当然也可以通过ssh客户端的配置文件来实现，这个倒是没试过！
# vim /etc/ssh/ssh_config //在最后添加以下内容，这个倒是没试过。 NumberOfPasswordPrompts 8
附录：
这种，对于以下这种，1次ssh连接尝试多次密码的，还有点效果
Jan 4 03:42:13 VM_*_*_centos sshd[16678]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=122.225.109.117 user=root Jan 4 03:42:14 VM_*_*_centos sshd[16809]: Failed password for root from 122.225.109.117 port 59570 ssh2 Jan 4 03:42:15 VM_*_*_centos sshd[16678]: Failed password for root from 122.225.109.117 port 58205 ssh2 Jan 4 03:42:16 VM_*_*_centos sshd[16678]: Failed password for root from 122.225.109.117 port 58205 ssh2 Jan 4 03:42:17 VM_*_*_centos sshd[16809]: Failed password for root from 122.225.109.117 port 59570 ssh2 Jan 4 03:42:19 VM_*_*_centos sshd[16809]: Failed password for root from 122.225.109.117 port 59570 ssh2 Jan 4 03:42:23 VM_*_*_centos sshd[16678]: Failed password for root from 122.225.109.117 port 58205 ssh2 Jan 4 03:42:27 VM_*_*_centos sshd[16810]: Disconnecting: Too many authentication failures for root
但对于这种，1次ssh连接只尝试1次密码的，感觉就没什么效果了。
Jan 6 09:58:09 VM_*_*_centos sshd[13825]: Failed password for root from 61.147.103.152 port 35896 ssh2 Jan 6 09:58:09 VM_*_*_centos sshd[13826]: Received disconnect from 61.147.103.152: 11: Normal Shutdown, Thank you for playing Jan 6 09:58:10 VM_*_*_centos sshd[13827]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=6 1.147.103.152 user=root Jan 6 09:58:12 VM_*_*_centos sshd[13827]: Failed password for root from 61.147.103.152 port 36516 ssh2 Jan 6 09:58:12 VM_*_*_centos sshd[13828]: Received disconnect from 61.147.103.152: 11: Normal Shutdown, Thank you for playing Jan 6 09:58:12 VM_*_*_centos sshd[13829]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=61.147.103.152 user=root