之前我曾经用shell脚本提取lastb登录失败超过指定次数的IP加入到iptables，来禁止这些IP登录主机，达到防止恶意攻击的目的。后来为了给主机提供更全面的防护，又安装了fail2ban。
今天早上我收到fail2ban发过来的报警邮件提示我禁止了一个IP登录，IP是219.235.4.22。我登录主机，输入last命令后，结果是这样的
root ssh:notty host-219-235-4-2 Thu Apr 23 19:32 - 19:32 (00:00)
root ssh:notty host-219-235-4-2 Thu Apr 23 19:32 - 19:32 (00:00)
root ssh:notty host-219-235-4-2 Thu Apr 23 19:32 - 19:32 (00:00)
root ssh:notty host-219-235-4-2 Thu Apr 23 19:32 - 19:32 (00:00)
root ssh:notty host-219-235-4-2 Thu Apr 23 19:32 - 19:32 (00:00)
root ssh:notty 61.160.247.150 Thu Apr 23 02:18 - 02:18 (00:00)
root ssh:notty 61.160.247.150 Thu Apr 23 02:18 - 02:18 (00:00)
root ssh:notty 61.160.247.150 Thu Apr 23 02:18 - 02:18 (00:00)
前面多了一个host，而且IP的分隔是用“－”，最后一位的IP地址无法显示出来。
我马上想到了查看fail2ban的日志，该日志默认是/var/log/secure
输入命令：
grep 'Failed password for root from' /var/log/secure|grep '219.235.4.22'
执行结果为：
Apr 23 19:32:27 localhost sshd[17856]: Failed password for root from 219.235.4.22 port 4993 ssh2
Apr 23 19:32:30 localhost sshd[17856]: Failed password for root from 219.235.4.22 port 4993 ssh2
Apr 23 19:32:31 localhost sshd[17856]: Failed password for root from 219.235.4.22 port 4993 ssh2
Apr 23 19:32:34 localhost sshd[17856]: Failed password for root from 219.235.4.22 port 4993 ssh2
Apr 23 19:32:36 localhost sshd[17856]: Failed password for root from 219.235.4.22 port 4993 ssh2
这时IP地址还有对方的端口都显示出来了，比lastb要详细的多。
这时我就把之前写的脚本修改了一下，直接读取/var/log/secure ：
#!/bin/bash
bad_ip=` grep 'Failed password for root from' /var/log/secure|awk '{print $11,$1,$2}'|sort|uniq -c|awk '$1>4 {print $2}'|xargs`
for ip in $bad_ip; do
in_iptables=`iptables -nvL|grep $ip |wc -l`
if [ $in_iptables -eq 0 ]; then
iptables -I INPUT -s $ip -j REJECT
service iptables save
fi
done
执行一下，成功！
