#关闭ipv6
net.ipv6.conf.all.disable_ipv6 = 1 
net.ipv6.conf.default.disable_ipv6 = 1

避免放大攻击

net.ipv4.icmp_echo_ignore_broadcasts = 1

开启恶意icmp错误消息保护

net.ipv4.icmp_ignore_bogus_error_responses = 1 #关闭路由转发 net.ipv4.ip_forward = 0 开起路由转发将0改为1即可 net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0 #开启反向路径过滤 net.ipv4.conf.all.rp_filter = 1 net.ipv4.conf.default.rp_filter = 1 #处理无源路由的包 net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0 #关闭sysrq功能 kernel.sysrq = 0 #core文件名中添加pid作为扩展名 kernel.core_uses_pid = 1

开启SYN洪水攻击保护

net.ipv4.tcp_syncookies = 1 表示开启SYN Cookies。当出现SYN等待队列溢出时，启用cookies来处理，可防范少量SYN攻击，默认为1，表示开启的； 表示SYN队列的长度，默认为1024，加大队列长度为8192，可以容纳更多等待连接的网络连接数 net.ipv4.tcp_max_syn_backlog = 262144 #修改消息队列长度 kernel.msgmnb = 65536 kernel.msgmax = 65536 #设置最大内存共享段大小bytes kernel.shmmax = 68719476736 kernel.shmall = 4294967296 #timewait的数量，默认180000 net.ipv4.tcp_max_tw_buckets = 6000 net.ipv4.tcp_sack = 1 net.ipv4.tcp_window_scaling = 1 net.ipv4.tcp_rmem = 4096  87380   4194304 TCP读buffer，可参考的优化值: 32768 436600 873200 net.ipv4.tcp_wmem = 4096  16384   4194304 tcp写buffer，可参考的优化值: 8192 436600 873200 net.core.wmem_default = 8388608 TCP写buffer的默认值 net.core.rmem_default = 8388608 TCP读buffer的默认值 net.core.rmem_max = 16777216 TCP写buffer的最大值 net.core.wmem_max = 16777216 TCP写buffer的最大值 #每个网络接口接收数据包的速率比内核处理这些包的速率快时，允许送到队列的数据包的最大数目 net.core.netdev_max_backlog = 262144
#限制仅仅是为了防止简单的DoS 攻击 net.ipv4.tcp_max_orphans = 3276800 #未收到客户端确认信息的连接请求的最大值 net.ipv4.tcp_max_syn_backlog = 262144 net.ipv4.tcp_timestamps = 0 #内核放弃建立连接之前发送SYNACK 包的数量 net.ipv4.tcp_synack_retries = 1 #内核放弃建立连接之前发送SYN 包的数量 net.ipv4.tcp_syn_retries = 1 #启用timewait 快速回收 net.ipv4.tcp_tw_recycle = 1 #开启重用。允许将TIME-WAIT sockets 重新用于新的TCP 连接 net.ipv4.tcp_tw_reuse = 1 net.ipv4.tcp_mem = 94500000 915000000 927000000 net.ipv4.tcp_fin_timeout = 1 #当keepalive 起用的时候，TCP 发送keepalive 消息的频度。缺省是2 小时 net.ipv4.tcp_keepalive_time = 30 #允许系统打开的端口范围 net.ipv4.ip_local_port_range = 1024    65000 #修改防火墙表大小，默认65536 #net.netfilter.nf_conntrack_max=655350 #net.netfilter.nf_conntrack_tcp_timeout_established=1200

确保无人能修改路由表

net.ipv4.conf.all.accept_redirects = 0 net.ipv4.conf.default.accept_redirects = 0 net.ipv4.conf.all.secure_redirects = 0 net.ipv4.conf.default.secure_redirects = 0

查看原文：http://www.chenqmc.com/?p=352