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Parent Category: Tutorials

Published: 28 October 2008

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           In this tutorial I'll show you how to install fail2ban on CentOS.

These are just installation notes and this should not be considered a complete howto.

The fail2ban script runs as a daemon and bans an IP address after too many failed login attempts. We use it for blocking failed login attempts for SSH, ProFTP and Postfix.

Fail2ban is very effective at stopping the brute-force attacks now common to all Internet-connected hosts. We have found it reliable and functional without causing problems.

Installation on Centos 5

wget http://superb-west.dl.sourceforge.net/sourceforge/fail2ban/fail2ban-0.8.1.tar.bz2

tar -xjvf fail2ban-0.8.1.tar.bz2

cd fail2ban-0.8.1

python setup.py install

Or you cand download the rpm for CentOS 5.x from: ftp://rpmfind.net/linux/dag/redhat/el5/en/i386/dag/RPMS/fail2ban-0.8.2-2.el5.rf.noarch.rpm and install:

rpm -ivh  fail2ban-0.8.2-2.el5.rf.noarch.rpm

vi /etc/fail2ban/jail.conf

Enable only the sections you need and do them one at a time. We enable SSH and ProFTP (both use /var/log/secure) as well as Postfix.

Set your local networks and any other networks you consider 'safe'. You certainly don't want to block your own clients!

ignoreip = 127.0.0.1 192.245.12.0/24 207.182.32.0/19 204.27.149.0/24

Installation on SME 7

NEEDS Python 2.4!! (NOT CURRENTLY AVAILABLE)

(SME 7 uses /var/log/messages)

Startup

cp files/redhat-initd /etc/init.d/fail2ban

chkconfig --add fail2ban

chkconfig fail2ban on

service fail2ban start

Tools

Show failed SSH logins by date:

cat /var/log/secure* | grep 'Failed password' | grep sshd | awk '{print $1,$2}' | sort | uniq -c

Search for correct log file:

grep such /var/log/messages*

grep ftp /var/log/messages*

grep -r NOQUEUE /var/log

This should match Postfix bans:

grep rejected /var/log/maillog

Configuration

Adjust the following sample configuration files to your needs.

# Fail2Ban jail.local configuration file

################################################

# www.starhost.ro

#

# The DEFAULT allows a global definition of the options. They can be override

# in each jail afterwards.

[DEFAULT]

# ignore Opus IP ranges

ignoreip = 127.0.0.1 192.245.12.0/24 207.182.32.0/19 204.27.149.0/24

# "bantime" is the number of seconds that a host is banned.

bantime = 600

# A host is banned if it has generated "maxretry" during the last "findtime"

# seconds.

findtime = 600

# "maxretry" is the number of failures before a host get banned.

maxretry = 3

# Don't know how well other backend options work.

backend = polling

[ssh-iptables]

enabled = true

filter = sshd

action = iptables[name=SSH, port=ssh, protocol=tcp]

sendmail-whois[name=SSH, dest= root@localhost, sender= This email address is being protected from spambots. You need JavaScript enabled to view it.]

logpath = /var/log/secure

maxretry = 3

[proftpd-iptables]

enabled = true

filter = proftpd

action = iptables[name=ProFTPD, port=ftp, protocol=tcp]

sendmail-whois[name=ProFTPD, dest= This email address is being protected from spambots. You need JavaScript enabled to view it., sender= This email address is being protected from spambots. You need JavaScript enabled to view it.]

logpath = /var/log/secure

maxretry = 3

[postfix]

enabled = true

filter = postfix

action = iptables[name=Postfix, port=smtp, protocol=tcp]

sendmail-whois[name=Postfix, dest= This email address is being protected from spambots. You need JavaScript enabled to view it., sender= This email address is being protected from spambots. You need JavaScript enabled to view it.]

logpath = /var/log/maillog

maxretry = 5

# Fail2Ban filter.d/postfix.local configuration file

################################################

# www.starhost.ro

#

[Definition]

failregex = reject: RCPT from (.*)\[<HOST>\]: 554

reject: RCPT from (.*)\[<HOST>\]: 550

reject: RCPT from (.*)\[<HOST>\]: 450

ignoreregex =

# Fail2Ban action.d/sendmail-whois.local configuration file

################################################

# www.starhost.ro

#

[Definition]

actionstart = echo -en "Subject: [Fail2Ban] <name>: started

From: Fail2Ban <<sender>>

To: <dest>\n

Hi,\n

The jail <name> has been started successfully.\n

Regards,\n

Fail2Ban" | /usr/sbin/sendmail -f <sender> <dest>

actionstop = echo -en "Subject: [Fail2Ban] <name>: stopped

From: Fail2Ban <<sender>>

To: <dest>\n

Hi,\n

The jail <name> has been stopped.\n

Regards,\n

Fail2Ban" | /usr/sbin/sendmail -f <sender> <dest>

actioncheck =

actionban = echo -en "Subject: [Fail2Ban] <name>: banned <ip>

From: Fail2Ban <<sender>>

To: <dest>\n

Hi,\n

The IP <ip> has just been banned by Fail2Ban after

<failures> attempts against <name>.\n\n

Here are more information about <ip>:\n

`/usr/bin/dig -x <ip>`\n

Regards,\n

Fail2Ban" | /usr/sbin/sendmail -f <sender> <dest>

actionunban =

[Init]

name = default

dest = root

sender = fail2ban

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