系统的INPUT和OUTPUT默认策略为DROP；
1、限制本地主机的web服务器在周一不允许访问；新请求的速率不能超过100个每秒；web服务器包含了admin字符串的页面不允许访问；web服务器仅允许响应报文离开本机；
系统默认策略设定：
~]# iptables -P INPUT DROP
~]# iptables -P OUPUT DROP
网络说明：
本地主机网段为192.168.150.0/24
web服务器IP为192.168.150.137
INPUT
~]# iptables -A INPUT -s 192.168.150.0/24 -d 192.168.150.137 -p tcp –dport 80 -m time –weekdays Mon –kerneltz -j DROP
~]# iptables -A INPUT -d 192.168.150.137 -p tcp –dport80 -m limit –limit 100/second -m state –state NEW -j ACCEPT
~]# iptables -A INPUT -s 192.168.150.0/24 -d 192.168.150.137 -p tcp –dport 80 -j ACCEPT
OUTPUT
~]# iptables -A OUTPUT -s 192.168.150.137 -d 0/0 -p tcp –sport 80 -m string –algo bm –string "admin" -j REJECT
~]# iptables -A OUTPUT -s 192.168.150.137 -d 0/0 -p tcp –sport 80 -m state –state ESTABLISHED -j ACCEPT
2、在工作时间，即周一到周五的8:30-18:00，开放本机的ftp服务给172.16.0.0网络中的主机访问；数据下载请求的次数每分钟不得超过5个；
INPUT:
#iptables -A INPUT -s 172.16.0.0/16 -p tcp –dport 21 -m time –timestart 08:30 –timestop 18:00 –weekdays Mon,Tue,Wed,Thu,Fri -m limit –limit-burst 5 –limit 5/minute -j ACCEPT
#iptables -A INPUT -m state –state ESTABLISHED,RELATED -j ACCEPT
OUTPUT
#iptables -A OUTPUT -p tcp -m multiport –sport 20,21 -m state –state ESTABLISHED,RELATED -j ACCEPT
3、开放本机的ssh服务给172.16.x.1-172.16.x.100中的主机，x为你的座位号，新请求建立的速率一分钟不得超过2个；仅允许响应报文通过其服务端口离开本机；
INPUT:
#iptables -A INPUT -d 172.16.100.6 -p tcp –dport 22 -m iprange –src-range 172.16.100.1-172.16.100.100 -m limit –limit 2/minute -j ACCEPT
OUTPUT:
# iptables -A OUTPUT -s 172.16.100.6 -p tcp –sport 22 -m iprange –dst-range 172.16.100.1-172.16.100.100 -m state –state ESTABLISHED -j ACCEPT
4、拒绝TCP标志位全部为1及全部为0的报文访问本机；
# iptabels -A INPUT -d 192.168.150.137 -p tcp –tcp-flags ALL ALL -j DROP
# iptables -A INPUT -d 192.168.150.137 -p tcp –tcp-flags ALL NONE -j DROP
5、允许本机ping别的主机；但不开放别的主机ping本机；
# iptables -A OUTPUT -s 192.168.150.138 -p icmp –icmp-type 8 -j ACCEPT 请求包
# iptables -A INPUT -d 192.168.150.138 -p icmp –icmp-type 0 -j ACCEPT 回包
6、判断下述规则的意义：
# iptables -N clean_in
创建自定义链clean_in
# iptables -A clean_in -d 255.255.255.255 -p icmp -j DROP 丢弃不定向广播ping包
# iptables -A clean_in -d 172.16.255.255 -p icmp -j DROP 丢弃定向广播ping包
禁止广播探测本网络主机在线情况
# iptables -A clean_in -p tcp ! –syn -m state –state NEW -j DROPQ 丢弃syn标志不为1的包和追踪状态为新连接的包
# iptables -A clean_in -p tcp –tcp-flags ALL ALL -j DROP 标志位全1的丢弃，全1肯定是不正常的包
# iptables -A clean_in -p tcp –tcp-flags ALL NONE -j DROP 标志位全0的丢弃，全0肯定是不正常的包
# iptables -A clean_in -d 172.16.100.7 -j RETURN 正常的报文RETURN
定义一个清理链
# iptables -A INPUT -d 172.16.100.7 -j clean_in 到目的主机的报文过来转给自定义链clean_in
# iptables -A INPUT -i lo -j ACCEPT 允许数据报文流入环回口
# iptables -A OUTPUT -o lo -j ACCEPT 允许数据报文流出环回口
开放本地环回口
# iptables -A INPUT -i eth0 -m multiport -p tcp –dports 53,113,135,137,139,445 -j DROP 指定流入报文接口为eth0，协议为tcp，目标端口为53,113,135,137,139,445，报文丢弃
# iptables -A INPUT -i eth0 -m multiport -p udp –dports 53,113,135,137,139,445 -j DROP 指定流入报文接口为eth0，协议为udp，目标端口为53,113,135,137,139,445，报文丢弃
# iptables -A INPUT -i eth0 -p udp –dport 1026 -j DROP 流入eth0的udp，端口为1026报文丢弃
# iptables -A INPUT -i eth0 -m multiport -p tcp –dports 1433,4899 -j DROP 流入eth0的tcp，端口为1433,4899报文丢弃
# iptables -A INPUT -p icmp -m limit –limit 10/second -j ACCEPT 限制ping包个数每秒最多10个
7、通过tcp_wrapper控制vsftpd仅允许172.16.0.0/255.255.0.0网络中的主机访问，但172.16.100.3除外；对所被被拒绝的访问尝试都记录在/var/log/tcp_wrapper.log日志文件中；
~]# vim /etc/hosts.allow
#
# hosts.allow This file contains access rules which are used to
# allow or deny connections to network services that
# either use the tcp_wrappers library or that have been
# started through a tcp_wrappers-enabled xinetd.
#
# See 'man 5 hosts_options' and 'man 5 hosts_access'
# for information on rule syntax.
# See 'man tcpd' for information on tcp_wrappers
#
vsftpd:192.168.150.0/255.255.255.0 EXCEPT 192.168.150.138
~]# vim /etc/hosts.deny
[root@localhost ~]# cat /etc/hosts.deny
#
# hosts.deny This file contains access rules which are used to
# deny connections to network services that either use
# the tcp_wrappers library or that have been
# started through a tcp_wrappers-enabled xinetd.
#
# The rules in this file can also be set up in
# /etc/hosts.allow with a 'deny' option instead.
#
# See 'man 5 hosts_options' and 'man 5 hosts_access'
# for information on rule syntax.
# See 'man tcpd' for information on tcp_wrappers
#
vsftpd:ALL :spawn /bin/echo `date` login attempt from %c to %s, %d >> /var/log/tcp_wrapper.log
执行结果
192.168.150.136主机
[root@localhost ~]# ftp 192.168.150.137
Connected to 192.168.150.137 (192.168.150.137).
220 (vsFTPd 3.0.2)
Name (192.168.150.137:root):
192.168.150.138主机
~]# ftp 192.168.150.137
Connected to 192.168.150.137 (192.168.150.137).
421 Service not available.
日志信息：
~]# cat /var/log/tcp_wrapper.log
2016年 12月 25日 星期日 16:41:17 CST login attempt from 192.168.150.138 to vsftpd@192.168.150.137, vsft
pd2016年 12月 25日 星期日 16:44:10 CST login attempt from 192.168.150.138 to vsftpd@192.168.150.137, vsft
pd
原创文章，作者：N23-苏州-void，如若转载，请注明出处：http://www.178linux.com/65032
评论列表（1条）
逻辑清晰，备注完整，非常好的作业。这篇作业题目实用性很强，你的完成程序非常好，相信在以后工作中会有很大帮助。