Q. mod_security supplies an array of request filtering and other security features to the Apache HTTP Server. How do I install mod_security under FreeBSD operating systems?

A. ModSecurity is an open source web application firewall that runs as an Apache module, and version 2.0 offers many new features and improvements.

It provides protection from a range of attacks against web applications and allows for HTTP traffic monitoring and real-time analysis with no changes to existing infrastructure. Some of the features include:

=> Parallel text matching
=> Geo IP resolution
=> Credit card number detection
=> Support for content injection
=> Automated rule updates
=> scripting as well as many others.

FreeBSD install mod_security

Type the following command to update ports tree:
# portsnap fetch update
Under FreeBSD 7, mod_security can be installed by typing the following commands:
# cd /usr/ports/www/mod_security
# make install clean

Configure mod_security

The modsecurity 2 Core Rules have been installed in
/usr/local/etc/apache22/Includes/mod_security2/

By default it run in “DetectionOnly” mode as not to disturb operatings of working websites and Apache. First change directory to /usr/local/etc/apache22/Includes/mod_security2/:
# cd /usr/local/etc/apache22/Includes/mod_security2/
Now, open the ModSecuirty core rule set file – modsecurity_crs_10_config.conf, enter:
# vi modsecurity_crs_10_config.conf
The file is well documented so just customize it according to your requirements. Open httpd.conf file located at /usr/local/etc/apache22 and make sure following line exists:
LoadFile /usr/local/lib/libxml2.so
LoadModule security2_module libexec/apache22/mod_security2.so

Finally, restart the apache:
# /usr/local/etc/rc.d/apache22 restart

Monitoring mod_security log files

By default logs are written to following two files:

• /var/log/httpd-modsec2_audit.log
• /var/log/httpd-modsec2_debug.log
• /var/log/httpd-error.log or virtual domain error.log file

You can detect attacks by viewing these two files using grep or tail:
tail -f /var/log/httpd-modsec2_audit.log
grep cmd.exe /var/log/httpd-modsec2_audit.log
tail -f /home/httpd/example.com/logs/error.log
Once everything started to working perfectly open modsecurity_crs_10_config.conf file and set SecRuleEngine to On:
SecRuleEngine On
Restart apache:
# /usr/local/etc/rc.d/apache22 restart

Further readings:

• Apache Security Book – The real strength of Apache Security lies in its wealth of interesting and practical advice, with many real-life examples and solutions in this book will save your life.
• Modsecurity project