当你的Linux服务器暴露在互联网之中，该服务器将会遭到互联网上的扫描软件进行扫描，并试图猜测SSH登录口令你会发现，每天会有多条SSH登录失败纪录。那些扫描工具将对你的服务器构成威胁，你必须设置复杂登录口令，并将尝试多次登录失败的IP给阻止掉，让其在一段时间内不能访问该服务器。简单方法也可以修改22端口号.

用DenyHosts可以阻止试图猜测SSH登录口令，它会分析/var/log/secure等日志文件，当发现同一IP在进行多次SSH密码尝试时就会记录IP到/etc/hosts.deny文件，从而达到自动屏蔽该IP的目的。last命令的信息来自/var/log/wtmp,如果对有经验的人可能会删除掉这个。但是还是会留下痕迹，使用nmap命令扫描端口，nmap -PO -sS ip,使用lsof命令，停掉一些不必要的服务，多关注漏洞，配置强有力的iptables来保护自己的系统或者尝试使用Chkrootkit应用程序对rootkit的跟踪，尝试AIDE来检查文件系统的完整性。服务器上除了root外，Linux用户越少越好，如果非要添加就添加shell为nologin。

免费下载地址在 http://linux.linuxidc.com/

用户名与密码都是www.it.net.cn

具体下载目录在 /2012年资料/3月/4/CentOS 6.0安装DenyHosts 2.6总结/
 
DenyHosts安装
1.下载denyhost官网为：http://denyhosts.sourceforge.net下载到/usr/src目录中，查询一下系统是否符合要求
[root@www.it.net.cn denyhosts]# ldd /usr/sbin/sshd|grep libwrap//查看libwrap动态链接库文件。
        libwrap.so.0 => /lib/libwrap.so.0 (0x006c8000)
[root@localhost denyhosts]# python -V//查询版本为2.6.5
Python 2.6.5
2.[root@www.it.net.cn DenyHosts-2.6]# python setup.py install//安装Denyhost
running install
running build
running build_py
creating build
creating build/lib
creating build/lib/DenyHosts
copying DenyHosts/version.py -> build/lib/DenyHosts
copying DenyHosts/purgecounter.py -> build/lib/DenyHosts
copying DenyHosts/regex.py -> build/lib/DenyHosts
copying DenyHosts/restricted.py -> build/lib/DenyHosts
copying DenyHosts/__init__.py -> build/lib/DenyHosts
copying DenyHosts/old-daemon.py -> build/lib/DenyHosts
copying DenyHosts/python_version.py -> build/lib/DenyHosts
copying DenyHosts/filetracker.py -> build/lib/DenyHosts
copying DenyHosts/plugin.py -> build/lib/DenyHosts
copying DenyHosts/constants.py -> build/lib/DenyHosts
copying DenyHosts/loginattempt.py -> build/lib/DenyHosts
copying DenyHosts/prefs.py -> build/lib/DenyHosts
copying DenyHosts/deny_hosts.py -> build/lib/DenyHosts
copying DenyHosts/lockfile.py -> build/lib/DenyHosts
copying DenyHosts/sync.py -> build/lib/DenyHosts
copying DenyHosts/allowedhosts.py -> build/lib/DenyHosts
copying DenyHosts/daemon.py -> build/lib/DenyHosts
copying DenyHosts/util.py -> build/lib/DenyHosts
copying DenyHosts/counter.py -> build/lib/DenyHosts
copying DenyHosts/denyfileutil.py -> build/lib/DenyHosts
copying DenyHosts/report.py -> build/lib/DenyHosts
running build_scripts
creating build/scripts-2.6
copying and adjusting denyhosts.py -> build/scripts-2.6
changing mode of build/scripts-2.6/denyhosts.py from 644 to 755
running install_lib
creating /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/version.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/purgecounter.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/regex.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/restricted.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/__init__.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/old-daemon.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/python_version.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/filetracker.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/plugin.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/constants.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/loginattempt.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/prefs.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/deny_hosts.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/lockfile.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/sync.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/allowedhosts.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/daemon.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/util.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/counter.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/denyfileutil.py -> /usr/lib/python2.6/site-packages/DenyHosts
copying build/lib/DenyHosts/report.py -> /usr/lib/python2.6/site-packages/DenyHosts
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/version.py to version.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/purgecounter.py to purgecounter.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/regex.py to regex.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/restricted.py to restricted.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/__init__.py to __init__.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/old-daemon.py to old-daemon.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/python_version.py to python_version.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/filetracker.py to filetracker.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/plugin.py to plugin.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/constants.py to constants.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/loginattempt.py to loginattempt.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/prefs.py to prefs.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/deny_hosts.py to deny_hosts.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/lockfile.py to lockfile.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/sync.py to sync.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/allowedhosts.py to allowedhosts.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/daemon.py to daemon.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/util.py to util.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/counter.py to counter.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/denyfileutil.py to denyfileutil.pyc
byte-compiling /usr/lib/python2.6/site-packages/DenyHosts/report.py to report.pyc
running install_scripts
copying build/scripts-2.6/denyhosts.py -> /usr/bin
changing mode of /usr/bin/denyhosts.py to 755
running install_data
creating /usr/share/denyhosts//在/usr/share目录创建denyhosts目录
copying denyhosts.cfg-dist -> /usr/share/denyhosts
copying setup.py -> /usr/share/denyhosts
copying daemon-control-dist -> /usr/share/denyhosts
copying CHANGELOG.txt -> /usr/share/denyhosts
copying README.txt -> /usr/share/denyhosts
creating /usr/share/denyhosts/scripts
copying scripts/restricted_from_passwd.py -> /usr/share/denyhosts/scripts
copying scripts/restricted_from_invalid.py -> /usr/share/denyhosts/scripts
creating /usr/share/denyhosts/plugins
copying plugins/README.contrib -> /usr/share/denyhosts/plugins
copying plugins/shorewall_deny.sh -> /usr/share/denyhosts/plugins
copying plugins/test_deny.py -> /usr/share/denyhosts/plugins
copying plugins/shorewall_allow.sh -> /usr/share/denyhosts/plugins
copying LICENSE.txt -> /usr/share/denyhosts
running install_egg_info
Writing /usr/lib/python2.6/site-packages/DenyHosts-2.6-py2.6.egg-info

3. [root@www.it.net.cn ~]#cd /usr/share/denyhosts/切换目录进入/usr/share/denyhosts目录
4.[root@www.it.net.cn denyhosts]# cp denyhosts.cfg.disk denyhosts.cfg//拷贝一份denyhosts.cfg
DenyHosts参数配置
SECURE_LOG = /var/log/secure#ssh日志文件
HOSTS_DENY = /etc/hosts.deny #将阻止IP写入到hosts.deny
PURGE_DENY =30m#过多久后清除已阻止IP
BLOCK_SERVICE  = sshd#阻止服务名
DENY_THRESHOLD_INVALID = 5//允许无效用户（在/etc/passwd未列出）登录失败次数,允许无效用户登录失败的次数.
DENY_THRESHOLD_VALID = 10#允许普通用户登录失败的次数
DENY_THRESHOLD_ROOT = 1//允许root登录失败的次数
DENY_THRESHOLD_RESTRICTED = 1#设定 deny host 写入到该资料夹  
WORK_DIR = /usr/share/denyhosts/data #将deny的host或ip纪录到Work_dir中
SUSPICIOUS_LOGIN_REPORT_ALLOWED_HOSTS=YES
HOSTNAME_LOOKUP=YES #是否做域名反解  
LOCK_FILE = /var/lock/subsys/denyhosts #将DenyHOts启动的pid纪录到LOCK_FILE中，已确保服务正确启动，防止同时启动多个服务。
ADMIN_EMAIL = enjoygoodboy@www.it.net.cn  #设置管理员邮件地址
SMTP_HOST = localhost
SMTP_PORT = 25
SMTP_FROM = DenyHosts <nobody@localhost>
SMTP_SUBJECT = DenyHosts Report
AGE_RESET_VALID=5d
AGE_RESET_ROOT=25d
AGE_RESET_RESTRICTED=25d
AGE_RESET_INVALID=10d
DAEMON_LOG = /var/log/denyhosts#自己的日志文件 
DAEMON_SLEEP = 30s
DAEMON_PURGE = 1h#该项与PURGE_DENY 设置成一样，也是清除hosts.deniedssh 用户的时间
 
5.DenyHosts启动文件配置
[root@www.it.net.cn denyhosts]# cp daemon-control-dist daemon-control
[root@www.it.net.cn denyhosts]# chown root daemon-control
[root@www.it.net.cn denyhosts]# chmod 700 daemon-control
[root@www.it.net.cn denyhosts]# ll
total 96
-rw-r--r-- 1 root root 16549 Dec  8  2006 CHANGELOG.txt
-rwx------ 1 root root  4076 Feb 27 18:38 daemon-control
-rwxr-xr-x 1 root root  4076 Apr 22  2006 daemon-control-dist
drwxr-xr-x 2 root root  4096 Feb 27 18:36 data
-rw-r--r-- 1 root root   777 Feb 27 16:44 denyhosts.cfg
-rw-r--r-- 1 root root 20830 Aug 20  2006 denyhosts.cfg-dist
-rw-r--r-- 1 root root 18009 Dec 17  2005 LICENSE.txt
drwxr-xr-x 2 root root  4096 Feb 27 16:36 plugins
-rw-r--r-- 1 root root  3575 Feb  3  2006 README.txt
drwxr-xr-x 2 root root  4096 Feb 27 16:36 scripts
-rw-r--r-- 1 root root  1522 Apr  5  2006 setup.py
[root@www.it.net.cn denyhosts]# ./daemon-control     #DenyHosts命令格式
Usage: ./daemon-control {start [args...] | stop | restart [args...] | status | debug | condrestart [args...] }
 
For a list of valid args refer to:
$ denyhosts.py --help
[root@www.it.net.cn denyhosts]# ./daemon-control start         #启动DenyHosts
starting DenyHosts:    /usr/bin/env python /usr/bin/denyhosts.py --daemon --config=/usr/share/denyhosts/denyhosts.cfg
如果要使DenyHosts每次重起后自动启动还需做如下设置：
[root@www.it.net.cn denyhosts]# ln -s /usr/share/denyhosts/daemon-control /etc/init.d/denyhosts//建立符号链接
[root@www.it.net.cn denyhosts]# chkconfig --add denyhosts//增加denyhosts服务进程

[root@www.it.net.cn denyhosts]# chkconfig  denyhosts on//设置开机启动denyhosts
[root@www.it.net.cn denyhosts]# chkconfig --list denyhosts
denyhosts       0:off   1:off   2:on    3:on    4:on    5:on    6:off
或者修改/etc/rc.local文件：
[root@www.it.net.cn denyhosts]# vi /etc/rc.local
加入下面这条命令
echo "/usr/share/denyhosts/daemon-control start">>/etc/rc.local
 
6.[root@www.it.net.cn denyhosts]# tail -f /var/log/secure
Feb 27 18:43:10 localhost login: pam_unix(login:auth): authentication failure; logname=LOGIN uid=0 euid=0 tty=tty1 ruser= rhost=  user=test
Feb 27 18:43:12 localhost login: FAILED LOGIN 1 FROM (null) FOR test, Authentication failure
Feb 27 18:43:15 localhost login: FAILED LOGIN 2 FROM (null) FOR test, Authentication failure
Feb 27 18:43:21 localhost login: FAILED LOGIN 3 FROM (null) FOR test, Authentication failure
Feb 27 18:43:26 localhost login: pam_unix(login:session): session opened for user test by LOGIN(uid=0)
Feb 27 18:43:26 localhost login: LOGIN ON tty1 BY test
Feb 27 18:45:32 localhost su: pam_unix(su:auth): authentication failure; logname=test uid=500 euid=0 tty=tty1 ruser=test rhost=  user=root
Feb 27 18:45:47 localhost su: pam_unix(su-l:session): session opened for user root by test(uid=500)
Feb 27 19:00:03 localhost sshd[19861]: Accepted password for root from 192.168.40.41 port 4289 ssh2