linux cc攻击检查,Linux DDos(SYN Flood)/CC攻击的检测和防范

netstat 工具来检测SYN攻击# netstat -n -p -t

tcp0 0 10.11.11.11:23124.173.152.8:25882 SYN_RECV-

tcp0 0 10.11.11.11:23236.15.133.204:2577 SYN_RECV-

tcp0 0 10.11.11.11:23127.160.6.129:51748 SYN_RECV-

LINUX系统中看到的，很多连接处于SYN_RECV状态(在WINDOWS系统中是SYN_RECEIVED状态)， 源IP地址都是随机的，表明这是一种带有IP欺骗的SYN攻击。# netstat -n -p -t | grep SYN_RECV | grep :80 | wc -l

324

查看在LINUX环境下某个端囗的未连接队列的条目数，显示TCP端囗22的未连接数有324个，虽然还远达不到系统极限，但应该引起管理员的注意。[root@pub wxjsr]# netstat -na | grep SYN_RECV

tcp 0 0 58.193.192.20:80 221.0.108.162:32383 SYN_RECV

tcp 0 0 58.193.192.20:80 125.85.118.231:2601 SYN_RECV

tcp 0 0 58.193.192.20:80 222.242.171.215:2696 SYN_RECV

tcp 0 0 58.193.192.20:80 116.52.10.51:2629 SYN_RECV

tcp 0 0 58.193.192.20:80 218.171.175.157:1117

[root@pub wxjsr]# netstat -na | grep SYN_RECV |wc

11 66 979

查看系统SYN相关的配置

Linux内核提供了若干SYN相关的配置，用命令： sysctl -a | grep syn[root@metc apache2]# /sbin/sysctl -a | grep syn

net.ipv6.conf.default.max_desync_factor = 600

net.ipv6.conf.all.max_desync_factor = 600

net.ipv6.conf.eth0.max_desync_factor = 600

net.ipv6.conf.lo.max_desync_factor = 600

net.ipv4.netfilter.ip_conntrack_tcp_timeout_syn_recv = 60

net.ipv4.netfilter.ip_conntrack_tcp_timeout_syn_sent = 120

net.ipv4.tcp_max_syn_backlog = 1280

net.ipv4.tcp_syncookies = 1

net.ipv4.tcp_synack_retries = 2

net.ipv4.tcp_syn_retries = 5

fs.quota.syncs = 18

防范SYN攻击设置

#缩短SYN- Timeout时间：iptables -A FORWARD -p tcp --syn -m limit --limit 1/s -j ACCEPT

iptables -A INPUT -i eth0 -m limit --limit 1/sec --limit-burst 5 -j ACCEPT

#每秒 最多3个 syn 封包 进入 表达为 ：iptables -N syn-flood

iptables -A INPUT -p tcp --syn -j syn-flood

iptables -A syn-flood -p tcp --syn -m limit --limit 1/s --limit-burst 3 -j RETURN

iptables -A syn-flood -j REJECT

#设置syncookies：sysctl -w net.ipv4.tcp_syncookies=1

/sbin/sysctl -w net.ipv4.tcp_max_syn_backlog=3000

/sbin/sysctl -w net.ipv4.tcp_synack_retries=1

/sbin/sysctl -w net.ipv4.tcp_syn_retries=1

sysctl -w net.ipv4.conf.all.send_redirects=0

sysctl -w net.ipv4.conf.all.accept_redirects=0

sysctl -w net.ipv4.conf.all.forwarding=0

/sbin/sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=1

/sbin/sysctl -w net.ipv4.conf.default.accept_source_route=0 # 禁用icmp源路由选项

/sbin/sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=1 # 忽略icmp ping广播包，应开启

/sbin/sysctl -w net.ipv4.icmp_echo_ignore_all=1 # 忽略所有icmp ping数据，覆盖上一项

转载：http://www.tuicool.com/articles/m6nE3q