A Bash shell script which uses ipset and iptables to ban a large number of IP addresses published in IP blacklists. ipset uses a hashtable to store/fetch IP addresses and thus the IP lookup is a lot faster than thousands of sequentially parsed iptables ban rules. However, the limit of an ipset list is 2^16 entries.

#!/bin/bash
IP_TMP=/tmp/ip.tmp
IP_BLACKLIST=/etc/ip-blacklist.conf
IP_BLACKLIST_TMP=/tmp/ip-blacklist.tmp
IP_BLACKLIST_CUSTOM=/etc/ip-blacklist-custom.conf # optional
list="chinese nigerian russian lacnic exploited-servers"
BLACKLISTS=(
"http://www.projecthoneypot.org/list_of_ips.php?t=d&rss=1" # Project Honey Pot Directory of Dictionary Attacker IPs
"http://check.torproject.org/cgi-bin/TorBulkExitList.py?ip=1.1.1.1"  # TOR Exit Nodes
"http://www.maxmind.com/en/anonymous_proxies" # MaxMind GeoIP Anonymous Proxies
"http://danger.rulez.sk/projects/bruteforceblocker/blist.php" # BruteForceBlocker IP List
"http://rules.emergingthreats.net/blockrules/rbn-ips.txt" # Emerging Threats - Russian Business Networks List
"http://www.spamhaus.org/drop/drop.lasso" # Spamhaus Don't Route Or Peer List (DROP)
"http://cinsscore.com/list/ci-badguys.txt" # C.I. Army Malicious IP List
"http://www.openbl.org/lists/base.txt"  # OpenBL.org 30 day List
"http://www.autoshun.org/files/shunlist.csv" # Autoshun Shun List
"http://lists.blocklist.de/lists/all.txt" # blocklist.de attackers
)
for i in "${BLACKLISTS[@]}"
do
    curl "$i" > $IP_TMP
    grep -Po '(?:\d{1,3}\.){3}\d{1,3}(?:/\d{1,2})?' $IP_TMP >> $IP_BLACKLIST_TMP
done
for i in `echo $list`; do
        # Download
        wget --quiet http://www.wizcrafts.net/$i-iptables-blocklist.html
        # Grep out all but ip blocks
        cat $i-iptables-blocklist.html | grep -v \< | grep -v \: | grep -v \; | grep -v \# | grep [0-9] > $i.txt
        # Consolidate blocks into master list
        cat $i.txt >> $IP_BLACKLIST_TMP
done

sort $IP_BLACKLIST_TMP -n | uniq > $IP_BLACKLIST
rm $IP_BLACKLIST_TMP
wc -l $IP_BLACKLIST

ipset flush blacklist
egrep -v "^#|^$" $IP_BLACKLIST | while IFS= read -r ip
do
        ipset add blacklist $ip
done

Installation

1. Copy update-blacklist.sh into /usr/local/bin
2. chmod +x /usr/local/bin/update-blacklist.sh
3. Modify update-blacklist.sh according to your needs. Per default, the blacklisted IP addresses will be saved to /etc/ip-blacklist.conf
4. apt-get install ipset
5. Create the ipset blacklist and insert it into your iptables input filter
6. Auto-update the blacklist using a cron job

iptables filter rule

ipset create blacklist hash:net hashsize 2000000 maxelem 2000000 (default value is 65000 and are inadequate for our use)
iptables -I INPUT -m set --match-set blacklist src -j DROP

Make sure to run this snippet in your firewall script. If you don’t, the ipset blacklist and the iptables rule to ban the blacklisted ip addresses will be missing!

Cron job

In order to auto-update the blacklist, copy the following code into /etc/cron.d/update-blacklist. Don’t update the list too often or some blacklist providers will ban your IP address. Once a day should be OK though.

59 23 * * *      root /usr/local/bin/update-blacklist.sh