Boy, when I started down the process of trying to get an IPS system setup, I had no idea what I was getting myself into.  I’m not much of a security guy or a linux guy, but I thought I’d give it a go.  I followed many different guides that all worked great for me, and thank you to those who put the following guides together: http://ubuntuforums.org/showthread.php?t=919472,  http://www.openmaniak.com/inline.php,  http://forum.learnit.vn/showthread.php?p=7007

Since I had an Ubuntu server disc, an Acer desktop with a Pentium D, 1GB of RAM an 3 nics (1 onboard and 2 100mb 3com’s) I thought I’d give it a go.  After a clean basic install of ubuntu 9.04 server, I ran the following to get it up to 9.10:

sudo apt-get install update-manager-core
sudo do-release-upgrade

The next step was installing all the dependencies:

sudo -i
apt-get -y install build-essential libpcap0.8-dev libmysqlclient15-dev /
mysql-client-5.0 mysql-server-5.0 bison flex apache2 libapache2-mod-php5 /
php5-gd php5-mysql libphp-adodb php-pear libc6-dev g++ gcc pcregrep /
libpcre3-dev iptables-dev bridge-utils

Next it was time to download and compile Snort and the rules:

cd /usr/src
wget http://dl.snort.org/snort-current/snort-2.8.5.2.tar.gz
tar zxvf snort-2.8.5.2.tar.gz
wget http://dl.snort.org/reg-rules/snortrules-snapshot-CURRENT.tar.gz
wget http://www.emergingthreats.net/rules/emerging.rules.tar.gz
cd snort-2.8.5.2
tar zxvf ../snortrules*
tar zxvf ../emerging*

./configure -enable-dynamicplugin --with-mysql --enabled-inline

make

make install

It should compile and make without any problems, if it does check out http://openmaniak.com/inline_pre.php for a good list of requirements.

It’s now time to get mysql ready:

mysql -u root -p

mysql> create database databasename;

mysql> grant all privileges on databasename.* to 'username'@'localhost' identified by 'password';

mysql> exit

Import the schema:

mysql -D databasename -u username -p < /usr/src/snort-2.8.5.2/schemas/create_mysql

Setup Snort:

cd /usr/src/snort-2.8.5.2

mkdir -p /etc/snort/rules /var/log/snort

cp etc/* /etc/snort/

cp rules/* /etc/snort/rules

Next up, editing the /etc/snort/snort.conf file:

1. Find var HOME_NET any and edit it to match your network(s) (var HOME_NET 192.168.0.0/16)
2. Find var EXTERNAL_NET any and change it to var EXTERNAL_NET !$HOME_NET
3. Find var RULE_PATH ../rules to var RULE_PATH /etc/snort/rules
4. I also added include $RULE_PATH/emerging.conf to read the emerging.conf rules file
5. Last, find the # output database: log, mysql, … and uncomment the line and change it to match your setup

Installing BASE:

First I upgraded and installed the required Pear modules:

pear upgrade-all

pear install Image_Color Image_Canvas-alpha Image_Graph-alpha

pear install Mail Mail_mime

Edit your /etc/php5/apache2/php.ini file and add under Dynamic Extensions:

extension=mysql.so

extension=gd.so

Restart Apache2:

/etc/init.d/apache2 restart

Download and setup BASE:

cd

wget http://sourceforge.net/projects/secureideas/files/BASE/base-1.4.4/base-1.4.4.tar.gz/download

cd /var/www

tar zxvf ~/base-1.4.4.tar.gz

mv base-1.4.4 base

cd base

cp -R /usr/src/snort-2.8.5.2/doc/signatures .

cd ..

chown -R www-data.www-data base

Go ahead and visit your site at http://yoursite/base and click continue:

• Step 1: enter /usr/share/php/adodb
• Step 2:  Database type = mysql; Database name = database name; Database host = localhost; Database username = username; Database Password = password
• Step 3: enter the name and password you’d like to use
• Step 4: click the Create BASE AG button
• Step 5: click Continue to go to the login screen

Bridging the Interfaces:

Load the bridge module:

modprobe bridge

Edit /etc/network/interfaces

# The loopback network interface

auto lo

iface lo inet loopback


# The primary network interface


auto eth2

iface eth2 inet static

        address 10.x.x.x

        netmask 255.x.x.x

        network 10.x.x.x

        broadcast 10.x.x.x

        gateway 10.x.x.x

        # dns-* options are implemented by the resolvconf package, if installed

        dns-nameservers 10.x.x.x

        dns-search searchbase


# The Bridge


auto br0

iface br0 inet manual

bridge_ports eth0 eth1

# Time to wait before loading bridge

bridge_maxwait 0

/etc/init.d/networking restart

Then setup the box to load the bridge kernel at startup:

crontab -e

@reboot root lsmod | grep bridge > /dev/null || /sbin/modprobe bridge;

The following is a startup script from http://openmaniak.com/inline_final.php that I used and modified for my setup.  I saved it in /etc/init.d/snortd:

#!/bin/bash

#

# snort_inline

start(){

# Start daemons.

echo "Starting ip_queue module:"

lsmod | grep ip_queue >/dev/null || /sbin/modprobe ip_queue;

#

echo "Starting iptables rules:"

# iptables traffic sent to the QUEUE:

# accept internal localhost connections

iptables -A INPUT -i lo -s 127.0.0.1 -d 127.0.0.1 -j ACCEPT

iptables -A OUTPUT -o lo -s 127.0.0.1 -d 127.0.0.1 -j ACCEPT

# send all the incoming, outgoing and forwarding traffic to the QUEUE

iptables -A INPUT -j QUEUE

iptables -A FORWARD -j QUEUE

iptables -A OUTPUT -j QUEUE

# Start Snort_inline

echo "Starting snort_inline: "

/usr/local/bin/snort_inline -c /etc/snort_inline/snort_inline.conf -Q -D -v 

-l /var/log/snort_inline

# -Q -> process the queued traffic

# -D -> run as a daemon

# -v -> verbose

# -l -> log path

# -c -> config path

}

stop() {

# Stop daemons.

# Stop Snort_Inline

# echo "Shutting down snort_inline: "

killall snort_inline

# Remove all the iptables rules and

# set the default Netfilter policies to accept

echo "Removing iptables rules:"

iptables -F

# -F -> flush iptables

iptables -P INPUT ACCEPT

iptables -P OUTPUT ACCEPT

iptables -P FORWARD ACCEPT

# -P -> default policy

}

restart(){

stop

start

}

case "$1" in

start)

start

;;

stop)

stop

;;

restart)

restart

;;

*)

echo $"Usage: $0 {start|stop|restart|}"

exit 1

esac

You can start snort with :

/etc/init.d/snortd start

And configure the server to run the snortd script at boot:

update-rc.d snortd defaults 95

And there we have it, what should be a functional Snort box compiled with inline support!  Wrapping my head around this has been a chore, I’m pleased that it’s at least running!  I haven’t put it in the middle of everything yet, so far I’ve just put it between my system and the network to play with rules.  One downside I found deals with restarting the snort process to load new rules; doing so will interrupt traffic until snort starts up again which can be around a minute or so.