Intrusion Detection using Snort

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This material is work-in-progress ...

Do not follow instructions here until this notice is removed.
(Last edited by Fab on 10 Jan 2013.)

This guide will set up (list subject to change):

  • Snort
  • Barnyard (maybe)
  • BASE

This guide will assume:

  • You have a knowledge of your network setup (at least know which subnets exist).
  • You have Alpine 2.0.2 installed and working with networking setup.
  • You have had at least three cups of coffee this morning. And not decaf.


Get Development Packages

Install Alpine and Pre-packaged components

apk add alpine-sdk mysql-dev php-mysql lighttpd php-xml php-pear libpcap-dev php-gd pcre-dev wireshark tcpdump tcpflow cvs bison flex

Download Non-Packaged Applications

Download the following packages

For the purpose of this document we will assume you download these files to /usr/src.

Download snort from We used version in this document.
Download the snort rules from
Download BASE from
Download adodb5 from

Compile Snort

Uncompress snort with something like:

tar -zxvf snort-

Then do the following:

cd snort- ./configure -enable-dynamicplugin --with-mysql make make install

Configure Snort and Ruleset

mkdir /etc/snort cd /etc/snort cp /usr/src/snort-* . mv /usr/src/snortrules-snapshot-2861.tar.gz /etc/snort/. tar -zxvf /usr/src/snortrules-snapshot-2861.tar.gz

Now edit the snort.conf file:

vi snort.conf

and change the following:

  • Change "var HOME_NET any" to "var HOME_NET X.X.X.X/X" (fill in the subnet with your trusted network)
  • Change "var EXTERNAL_NET any" to "var EXTERNAL_NET !$HOME_NET" (this is stating everything except HOME_NET is external)
  • Change "var RULE_PATH ../rules" to "var RULE_PATH /etc/snort/rules"
  • Change "var SO_RULE_PATH ../so_rules" to "var SO_RULE_PATH /etc/snort/so_rules"
  • Change "var PREPROC_RULE_PATH ../preproc_rules" to "var PREPROC_RULE_PATH /etc/snort/preproc_rules"
  • Comment out the line that says "dynamicdetection directory /usr/local/lib/snort_dynamicrules" (by placing a "#" in front of the line)
  • Scroll down the list to the section with "# output database: log, ..." and remove the "#" from in front of this line.
  • Edit this line to look like this:
output database: log, mysql, user=root password=yoursecretpassword dbname=snort host=localhost
  • Make note of the username, password, and dbname. You will need this information when we set up mysql.
  • Find this line (line 194 in current version)
preprocessor http_inspect: global iis_unicode_map 1252 compress_depth 20480 decompress_depth 20480
and remove from "compress_depth" to the end of the line. When done, the line will read:
preprocessor http_inspect: global iis_unicode_map 1252
  • Find this line (line 207 in current version)
inspect_gzip \
and remove it.
  • Save and quit.

Start and Setup MySQL

(Need to add detail here on starting up MySQL for the first time)

/usr/bin/mysql_install_db --user=mysql rc-update add mysql /etc/init.d/mysql start /usr/bin/mysqladmin -u root password 'password' (set password to the same password you specified in the snort.conf file) mysql -u root -p

Once in mysql, type the following commands:

mysql> create database snort; mysql> exit

Now create the database schema:

mysql -D snort -u root -p < /usr/src/snort-

Configure PHP and PEAR

Edit /etc/php/php.ini and add the following under "Dynamic Extensions".

Save and exit. From the command line, type the following:

pear install Image_Color pear install Image_Canvas-alpha pear install Image_Graph-alpha pear install mail pear install mail_mime

Start Apache or lighttpd

Need to decide which of these to use in production.

Setup BASE


mv /usr/src/adodb5 /var/www/localhost/htdocs/. mv /usr/src/base-1.4.5/* /var/www/localhost/htdocs/.

Now, open your web browser and navigate to http://X.X.X.X/setup (where x.x.x.x is your server's IP address)

Click continue on the first page.
Step 1 of 5: Enter the path to ADODB.
This is /var/www/localhost/htdocs/adodb5.
Step 2 of 5:
Database type = MySQL, Database name = snort, Database Host = localhost, Database username = root, Database Password = YOUR_PASSWORD
Step 3 of 5: If you want to use authentication enter a username and password here.
Step 4 of 5: Click on Create BASE AG.
Step 5 of 5: one step 4 is done at the bottom click on Now continue to step 5.
Copy the text on the screen, and then paste into a new file named /var/www/localhost/htdocs/base_conf.php. Save that file.

Configure Barnyard

To improve performance.