ipset-blacklist

A tiny 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.

The ipset command doesn't work under OpenVZ. It works fine on dedicated and fully virtualized servers like KVM though.

What's new

• 08/15/2017: Filtering default gateway and multicast ranges
• 01/20/2017: Ignoring "Service unavailable" HTTP status code, removed IGNORE_CURL_ERRORS
• 11/04/2016: Documentation added to show how to prevent fail2ban from inserting its rules above the ipset-blacklist when restarting the fail2ban service
• 11/11/2015: Merged all suggestions from https://github.com/drzraf
• 10/24/2015: Outsourced the entire configuration in it's own configuration file. Makes updating the shell script way easier!
• 10/22/2015: Changed the documentation, the script should be put in /usr/local/sbin not /usr/local/bin

Quick start for Debian/Ubuntu based installations

1. wget -O /usr/local/sbin/update-blacklist.sh https://raw.githubusercontent.com/trick77/ipset-blacklist/master/update-blacklist.sh
2. chmod +x /usr/local/sbin/update-blacklist.sh
3. mkdir -p /etc/ipset-blacklist ; wget -O /etc/ipset-blacklist/ipset-blacklist.conf https://raw.githubusercontent.com/trick77/ipset-blacklist/master/ipset-blacklist.conf
4. Modify ipset-blacklist.conf according to your needs. Per default, the blacklisted IP addresses will be saved to /etc/ipset-blacklist/ip-blacklist.restore
5. apt-get install ipset
6. Create the ipset blacklist and insert it into your iptables input filter (see below). After proper testing, make sure to persist it in your firewall script or similar or the rules will be lost after the next reboot.
7. Auto-update the blacklist using a cron job

iptables filter rule

# Enable blacklists
ipset restore < /etc/ipset-blacklist/ip-blacklist.restore
iptables -I INPUT 1 -m set --match-set blacklist src -j DROP

Make sure to run this snippet in a firewall script or just insert it to /etc/rc.local.

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.

PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root
33 23 * * *      root /usr/local/sbin/update-blacklist.sh /etc/ipset-blacklist/ipset-blacklist.conf

Check for dropped packets

Using iptables, you can check how many packets got dropped using the blacklist:

drfalken@wopr:~# iptables -L INPUT -v --line-numbers
Chain INPUT (policy DROP 60 packets, 17733 bytes)
num   pkts bytes target            prot opt in  out source   destination
1       15  1349 DROP              all  --  any any anywhere anywhere     match-set blacklist src
2        0     0 fail2ban-vsftpd   tcp  --  any any anywhere anywhere     multiport dports ftp,ftp-data,ftps,ftps-data
3      912 69233 fail2ban-ssh-ddos tcp  --  any any anywhere anywhere     multiport dports ssh
4      912 69233 fail2ban-ssh      tcp  --  any any anywhere anywhere     multiport dports ssh

Since iptable rules are parsed sequentally, the ipset-blacklist is most effective if it's the topmost rule in iptable's INPUT chain. However, restarting fail2ban usually leads to a situation, where fail2ban inserts its rules above our blacklist drop rule. To prevent this from happening we have to tell fail2ban to insert its rules at the 2nd position. Since the iptables-multiport action is the default ban-action we have to add a file to /etc/fail2ban/action.d:

tee << EOF /etc/fail2ban/action.d/iptables-multiport.local
[Definition]
actionstart = <iptables> -N f2b-<name>
              <iptables> -A f2b-<name> -j <returntype>
              <iptables> -I <chain> 2 -p <protocol> -m multiport --dports <port> -j f2b-<name>
EOF

(Please keep in in mind this is entirely optional, it just makes dropping blacklisted IP addresses most effective)

Modify the blacklists you want to use

Edit the BLACKLIST array in /etc/ipset-blacklist/ipset-blacklist.conf to add or remove blacklists, or use it to add your own blacklists.

BLACKLISTS=(
"http://www.mysite.me/files/mycustomblacklist.txt" # Your personal blacklist
"http://www.projecthoneypot.org/list_of_ips.php?t=d&rss=1" # Project Honey Pot Directory of Dictionary Attacker IPs
# I don't want this: "http://www.openbl.org/lists/base.txt"  # OpenBL.org 30 day List
)

If you for some reason want to ban all IP addresses from a certain country, have a look at IPverse.net's aggregated IP lists which you can simply add to the BLACKLISTS variable. For a ton of spam and malware related blacklists, check out this github repo: https://github.com/firehol/blocklist-ipsets

Troubleshooting

Set blacklist-tmp is full, maxelem 65536 reached
Increase the ipset list capacity. For instance, if you want to store up to 80,000 entries, add these lines to your ipset-blacklist.conf:

MAXELEM=80000

ipset v6.20.1: Error in line 2: Set cannot be created: set with the same name already exists
If this happens after changing the MAXELEM parameter: ipset seems to be unable to recreate an exising list with a different size. You will have to solve this manually by deleting and inserting the blacklist in ipset and iptables. A reboot will help as well and may be easier. You may want to remove /etc/ipset-blacklist/ip-blacklist.restore too because it may still contain the old MAXELEM size.

ipset v6.12: No command specified: unknown argument -file You're using an outdated version of ipset which is not supported.