DenyHosts是用python2.3编写的一个程序，会分析/var/log/secure等文件，当发现同一个ip进行多次ssh登录失败时会将其写入/etc/hosts.dengy文件，达到屏蔽该ip的目的。

下载DenyHosts包

[root@localhost ~]# wget http://jaist.dl.sourceforge.net/project/denyhosts/denyhosts/2.6/DenyHosts-2.6.tar.gz

安装DenyHosts

[root@localhost ~]# tar xf DenyHosts-2.6.tar.gz
[root@localhost ~]# cd DenyHosts-2.6
[root@localhost DenyHosts-2.6]# python setup.py install

制作配置文件

[root@localhost DenyHosts-2.6]# cp denyhosts.cfg-dist /etc/denyhosts.cfg
[root@localhost DenyHosts-2.6]# cp daemon-control-dist daemon-control
[root@localhost DenyHosts-2.6]# chown root daemon-control
[root@localhost DenyHosts-2.6]# chmod 700 daemon-control

修改配置文件

将daemon-control中的#DENYHOSTS_CFG = "/usr/share/denyhosts/denyhosts.cfg"改为 DENYHOSTS_CFG = "/etc/denyhosts.cfg"

启动

[root@localhost DenyHosts-2.6]# ./daemon-control start（注意相对路径）

测试另外一台服务器远程连接172.16.1.16

默认允许五次，测试发现登陆失败五次之后不允许登陆

[root@localhost ~]# ssh [email protected]
[email protected]'s password: 
Permission denied, please try again.
[email protected]'s password: 
Permission denied, please try again.
[email protected]'s password: 
Permission denied (publickey,gssapi-keyex,gssapi-with-mic,password).
[root@localhost ~]# 
[root@localhost ~]# ssh [email protected]
[email protected]'s password: 
Permission denied, please try again.
[email protected]'s password: 
Permission denied, please try again.
[email protected]'s password: 
Permission denied (publickey,gssapi-keyex,gssapi-with-mic,password).
[root@localhost ~]# ssh [email protected]
[email protected]'s password: 
Permission denied, please try again.
[email protected]'s password: 
Permission denied, please try again.
[email protected]'s password: 
Permission denied (publickey,gssapi-keyex,gssapi-with-mic,password).
[root@localhost ~]# ssh [email protected]
[email protected]'s password: 
Permission denied, please try again.
[email protected]'s password: 
Permission denied, please try again.
[email protected]'s password: 
Permission denied (publickey,gssapi-keyex,gssapi-with-mic,password).
[root@localhost ~]# ssh [email protected]
ssh_exchange_identification: read: Connection reset by peer

查看hosts.deny文件

登陆连续失败之后就会把ip地址写在hosts.deny文件

如果要使DenyHosts每次重起后自动启动还需做如下设置：
# ln -sf /usr/share/denyhosts/daemon-control /etc/init.d/denyhosts
# chkconfig --add denyhosts
# chkconfig --level 2345 denyhosts on
或者执行下面的命令加入开机启动，将会修改/etc/rc.local文件：
# echo "/usr/share/denyhosts/daemon-control start" >> /etc/rc.local

DenyHosts配置文件/usr/share/denyhosts/denyhosts.cfg说明：

SECURE_LOG = /var/log/secure
#sshd日志文件，它是根据这个文件来判断的，不同的操作系统，文件名稍有不同。

HOSTS_DENY = /etc/hosts.deny