Fetch a list of known brute force attackers from badips.com and apply/update iptables DROP rules

block_badips.sh

#!/bin/bash
# This script downloads a list of IPs known for brute force attacking within the last two weeks.
# The fetched IPs get blocked with iptables with the special comment "BADIP". This script only
# modifies iptables rules with that comment. This measure makes it well compatible with other firewall
# scripts like the SUSEFirewall.
# The iptables rules are updated every time this script is executed. Additionally this script is
# quiet on stdout, which makes it well suited for being executed as a cronjob.
#
# Please also use fail2ban with the badips modification and help to maintain the list of attackers.
# See also: fail2ban and http:///www.badips.com

IPTABLES_BIN=/usr/sbin/iptables
IPTABLES_SAVE_BIN=/usr/sbin/iptables-save

LOGGER_OPTS="-t add_badips"

# fetch IP list from badips.com
URL="http://www.badips.com/get/list/ssh/2?age=2w"

### download
logger $LOGGER_OPTS "fetching list of bad IPs from $URL"
FILE=`mktemp`
# curl or wget can be used to download. Uncomment line which one should be used
curl -s $URL > $FILE
#wget -q -O $FILE $URL
if [ $? -ne 0 ]; then 
        logger $LOGGER_OPTS -s "ERROR: download of $URL failed"
        exit 1
else
        logger $LOGGER_OPTS "got "`wc -l $FILE | awk '{ print $1 }'` " IPs"
fi
  
### remove old blocked entries
FILE2=`mktemp`
# export all rules with comment "BADIP"
$IPTABLES_SAVE_BIN  | grep -e "--comment BADIP" | sed 's/-A/-D/' > $FILE2
logger $LOGGER_OPTS "removing "`wc -l $FILE2 | awk '{ print $1 }'` " old entries"
# remove all IPs previously known as bad
# HINT: use a while loop here since a for loop would require changing the IFS due to spaces in $FILE2
while read RULE; do
        $IPTABLES_BIN $RULE
done < $FILE2
rm $FILE2

### add new IPs
for IP in $(cat $FILE); do
        $IPTABLES_BIN -I INPUT $RULE -s $IP -j DROP -m comment --comment "BADIP"
done
rm $FILE
logger $LOGGER_OPTS "done applying IPs"

Is this approach safe because of high number of IPs in iptables?