一、安装依赖包：
yum install perl-libwww-perl perl iptables
二、下载并安装 CSF：
wget http://www.configserver.com/free/csf.tgz
tar -xzf csf.tgz
cd csf
sh install.sh
三、测试 CSF 是否能正常工作:
[root@localhost csf]# perl /etc/csf/csftest.pl
Testing ip_tables/iptable_filter…OK
Testing ipt_LOG…OK
Testing ipt_multiport/xt_multiport…OK
Testing ipt_REJECT…OK
Testing ipt_state/xt_state…OK
Testing ipt_limit/xt_limit…OK
Testing ipt_recent…OK
Testing xt_connlimit…OK
Testing ipt_owner/xt_owner…OK
Testing iptable_nat/ipt_REDIRECT…OK
Testing iptable_nat/ipt_DNAT…OK
RESULT: csf should function on this server
csf的配置：
CSF的配置文件是 /etc/csf/csf.conf
# Allow incoming TCP ports
# 推荐您更改 SSH 的默认端口（22）为其他端口，但请注意一定要把新的端口加到下一行中
TCP_IN = “20,21,47,81,1723,25,53,80,110,143,443,465,587,993,995″
# Allow outgoing TCP ports同上，把 SSH 的登录端口加到下一行。
# 在某些程序要求打开一定范围的端口的情况下，例如Pureftpd的passive mode，可使用类似 30000:35000 的方式打开30000-35000范围的端口。
TCP_OUT = “20,21,47,81,1723,25,53,80,110,113,443″
# Allow incoming UDP ports
UDP_IN = “20,21,53″
# Allow outgoing UDP ports
# To allow outgoing traceroute add 33434:33523 to this list
UDP_OUT = “20,21,53,113,123″
# Allow incoming PING 是否允许别人ping你的服务器，默认为1，允许。0为不允许。
ICMP_IN = “1″
以上这些配置大家一看就懂了，下面再介绍几个比较常用的：
免疫某些类型的小规模 DDos 攻击：
# Connection Tracking. This option enables tracking of all connections from IP
# addresses to the server. If the total number of connections is greater than
# this value then the offending IP address is blocked. This can be used to help
# prevent some types of DOS attack.
#
# Care should be taken with this option. It’s entirely possible that you will
# see false-positives. Some protocols can be connection hungry, e.g. FTP, IMAPD
# and HTTP so it could be quite easy to trigger, especially with a lot of
# closed connections in TIME_WAIT. However, for a server that is prone to DOS
# attacks this may be very useful. A reasonable setting for this option might
# be arround 200.
#
# To disable this feature, set this to 0
CT_LIMIT = “200″##固定时间内同一个IP请求的此数
# Connection Tracking interval. Set this to the the number of seconds between
# connection tracking scans
CT_INTERVAL = “30″ ##指上面的固定时间，单位为秒
# Send an email alert if an IP address is blocked due to connection tracking
CT_EMAIL_ALERT = “1″ ##是否发送邮件
# If you want to make IP blocks permanent then set this to 1, otherwise blocks
# will be temporary and will be cleared after CT_BLOCK_TIME seconds
# 是否对可疑IP采取永久屏蔽，默认为0，即临时性屏蔽。
CT_PERMANENT = “0″
# If you opt for temporary IP blocks for CT, then the following is the interval
# in seconds that the IP will remained blocked for (e.g. 1800 = 30 mins)
# 临时性屏蔽时间
CT_BLOCK_TIME = “1800″
# If you don’t want to count the TIME_WAIT state against the connection count
# then set the following to “1″
CT_SKIP_TIME_WAIT = “0″ ##是否统计TIME_WAIT链接状态
# If you only want to count specific states (e.g. SYN_RECV) then add the states
# to the following as a comma separated list. E.g. “SYN_RECV,TIME_WAIT”
# Leave this option empty to count all states against CT_LIMIT
CT_STATES = “” ##是否分国家来统计，填写的是国家名
# If you only want to count specific ports (e.g. 80,443) then add the ports
# to the following as a comma separated list. E.g. “80,443″
#
# Leave this option empty to count all ports against CT_LIMIT
# 对什么端口进行检测，为空则检测所有，防止ssh的话可以为空，统计所有的。
CT_PORTS = “”
楼主你好，楼下再见，，睡觉
