一个小时内同一IP请求连接次数超过5次，封IP 1个小时。
同时，限制发起请求的IP段
# cat /etc/sysconfig/iptables
# Firewall configuration written by system-config-firewall
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
#-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
-N Recent_Block
-A Recent_Block -p tcp --dport 22 -m state --state NEW -m recent --name SSHPOOL --rcheck --seconds 3600 --hitcount 5 -j DROP
-A Recent_Block -p tcp --dport 22 -m state --state NEW -m recent --name SSHPOOL --set -j ACCEPT
-A INPUT -s 192.168.0.0/24 -p tcp --dport 22 -j Recent_Block
-A INPUT -s 192.168.1.0/24 -p tcp --dport 22 -j Recent_Block
-A INPUT -s 192.168.2.0/24 -p tcp --dport 22 -j Recent_Block
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT
访问日志的路径是：
/proc/net/xt_recent/SSHPOOL
