解析：shell结合iptables自动拒绝恶意连接ssh

#!/bin/bash
while [ 1 ]

do
#设置脚本运行间隔时间（单位秒）
EXEC_TIME=60

#设置连接出错次数
NUMBER=5

#邮件报警地址设置
MAILFROM=monitor@x.x.x.x.com
MAILTO=x.x.x.x@jb200.com

#设置释放锁定IP时间(单位秒）
RETIME=3000

#本机IP地址设置，邮件报警时用
IPADDR=192.168.0.91

#设置获取的IP地址的存放位置
BADIP=/tmp/.ssh/.ssh_badip
BKIP=/tmp/.ssh/.back_ssh_badip
mkdir /tmp/.ssh 2>/dev/null
touch $BADIP $BKIP
LOG=/var/log/messages

#获取sshd服务端口
SSHPORT=`netstat -antlp |grep sshd |awk -F: ‘{print $4}’|sed -n ’1p’`

TIME=`date +”%Y-%m-%d %H:%M:%S”`
IPTFILE=/tmp/.ssh/.iptables
IPLIST=/tmp/.ssh/.iplist
touch $IPTFILE $IPLIST
LINEA=`grep -v 日期$BKIP| wc -l |awk ‘{print $1}’`

echo ” “”日 期”" “”时 间”" “”连接次数”" “”IP 地 址”" “”日期”" “”小时” > $BADIP ;lastb -i | awk ‘{print $3″ “$6″ “$7}’ | awk -F: ‘{print $1}’ |sort |uniq -c|awk ‘$1 > ‘$NUMBER’ {print $1″ ” $2″ “$3″ “$4}’| awk -vtime=”$TIME” ‘{print time” “$1 ” “$2″ “$3″ “$4}’|column -t >>$BADIP

cat $BADIP >> $BKIP

DROPIP=`cat $BADIP | wc -l `

ipline=/tmp/.ssh/.ipline

touch $ipline

if [ $DROPIP -gt 1 ] ; then

for bip in `grep -v 日期$BADIP | awk ‘{print $4}’`

do

IPLINEA=`/sbin/iptables -L -n –line-number |egrep ‘[DROP|22]‘ | grep -v Ch |awk ‘{print $1}’|wc -l`

echo $IPLINEA > $ipline

iptables -I INPUT -s $bip -p tcp –dport $SSHPORT -j DROP

echo $bip >> $IPLIST

echo “$TIME Lock IP address $bip iptables ” >> $LOG

cat /var/log/btmp >> /var/log/btmp.bak ; >/var/log/btmp

TIME_NOWA=`date +%s`

echo $TIME_NOWA > time

done

fi

LINEVE=`wc -l /tmp/.ssh/.ipline | awk ‘{print $1}’ `

if [ $LINEVE -gt 0 ] ; then

echo linefile ok > /dev/null

else

echo 0 > $ipline

fi

IPLINE=`cat $ipline`

LINEB=`grep -v 日期$BKIP|wc -l |awk ‘{print $1}’`

VALUE=`echo “$LINEB-$LINEA”|bc`

#获取被列入$BKIP的ip地址

LAST=`tail -n $VALUE $BKIP`

if [ $VALUE -gt 0 ] ; then

sendmail -t <<EOF

from: $MAILFROM

to: $MAILTO

subject: 严重警告

$time 当前有人正在试探性连接SSH服务，系统已拦截，查看详情请登录服务器$IPADDR 。

$LAST

EOF

echo “$TIME send mail to $MAILTO” >> $LOG

fi

IPLINEB=`/sbin/iptables -L -n –line-number |egrep ‘[DROP|22]‘ | grep -v Ch |awk ‘{print $1}’|wc -l`

if [ $IPLINEB -eq 1 ] ; then

IPLINEB=`/sbin/iptables -L -n –line-number |egrep ‘[DROP|22]‘ | grep -v Ch |awk ‘{print $1}’|wc -l >/dev/null ; echo “$IPLINEB+1″|bc `

fi

#当前时间

OLD_TIME=`cat time`

TIME_NOWB=`date +%s`

#间隔时间判断

TIME_IN=`echo “$TIME_NOWB-$OLD_TIME” | bc`

#删除禁止的IP地址

LNUMBER=`echo “$IPLINEB-$IPLINE”|bc`

if [ $LNUMBER -lt 2 ] ; then

LNUMBER=`echo “$IPLINEB-$IPLINE+2″|bc`

else

LNUMBER=`echo “$IPLINEB-$IPLINE”|bc`

fi

if [ $LNUMBER -gt 1 ] ; then

if [ $TIME_IN -gt $RETIME ] ; then

iptables -L -n –line-number | awk ‘{print $5″ “$2″ “$1″ “$8}’ | awk -Fdpt: ‘{print $1″ “$2}’ | egrep -v ‘[num|Ch]‘ | grep $SSHPORT|column -t > $IPTFILE

RMIP=`cat $IPLIST |awk ‘{print $1}’`

for i in `awk ‘NR==FNR{a[$1]=$2″ “$3″ “$4}NR>FNR{print $0,a[$1]}’ $IPTFILE $IPLIST | awk ‘{print $3}’`

do

iptables -D INPUT $i

>$IPLIST

echo “$TIME Remove lock $RMIP IP address ” >> $LOG

done

fi

fi

#ps aux | grep ./ssh |grep -v ‘/usr/sbin/sshd’ |grep -v grep |awk ‘{print $2}’ >> $LOG

sleep $EXEC_TIME

done