用hosts.deny拒绝ssh试探连接

主要是为了考虑到在公网打开ssh后，不断有人试探连接，自动实现拒绝。
#!/bin/bash
#自动监控ssh试探登陆,添加在/etc/hosts.deny实现拒绝

#设置尝试次数,尝试操作3次，就实现拒绝连接
number=3

#设置运行间隔时间,单位秒
sleep=1

#设置锁定试探IP地址时间，单位秒
locktime=15

lockfile=/tmp/lock-ipadd
touch $lockfile

while true
do

#执行锁定检查
for badip in `lastb  |awk '{print $3}' |grep -v ^$  |grep -v [A-Z] |sort |uniq -c |awk -vn="$number" '$1 > n {print $2}' `
do
   time=`date +%s`
   bip=`echo $badip |head -n $i |tail -n1`
   echo $bip |grep [0-9] &>/dev/null

   if [ $? -eq 0 ] ; then

       grep $bip $lockfile &>/dev/null

       if [ $? -eq 1 ] ; then
          echo $bip.$time >>$lockfile
       fi

       grep $bip /etc/hosts.deny &>/dev/null
       [ ! $? -eq 0 ] && (echo "SSHD:$bip" >>/etc/hosts.deny; logger "lock ip address $bip ")
       cat /var/log/btmp >> /var/log/btmp.bak
       >/var/log/btmp
   fi
done

#解除锁定操作
nowtime=`date +%s`
rows=`wc -l  $lockfile |awk '{print $1}' `
for (( i=1;i<=rows;i++))
do
       line=`cat -n $lockfile |head -n $i |tail -n1 |awk -F. '{print $5" "$1}' |awk -vt="$nowtime" '{print t-$1" "$2}' |awk -vt="$locktime" '$1>t {print $2}'`
       echo $line |grep [0-9] &>/dev/null
    if [ $? -eq 0 ] ; then
       unlockip=`cat -n $lockfile |column -t | grep ^$line |awk '{print $2}' | awk -F. '{print $1"."$2"."$3"."$4}'`
       sed -i "/SSHD:$unlockip/d" /etc/hosts.deny
       logger "unlock ip address $unlockip "
       sed -i "/$unlockip/d" $lockfile
    fi
done

   sleep $sleep

done

日志查看
tail /var/log/messages
Apr  6 19:49:58 localhost sess: lock ip address 192.168.0.155
Apr  6 19:50:47 localhost sess: unlock ip address 192.168.0.12
Apr  6 19:51:02 localhost sess: unlock ip address 192.168.0.37