rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-3.noarch.rpm
Install via yum.
yum install mod_security
This will load your basic mod_security configuration including the core rules.
Next I had to set SecDataDir in the config. This was not initially set and errors in the following form appeared in the log file.
ModSecurity: Unable to retrieve collection (name "
", key " "). Use SecDataDir to define data directory first.
Fixed this up by creating SecDataDir and creating a directory for this purpose, making sure to give apache permission to use it.
( Added SecDataDir /usr/local/apache/modsec_data )
chown apache:apache /usr/local/apache/modsec_data
chown apache:apache /usr/local/apache
After a restart modsecurity successfully began applying rules, but rather than blocking problem requests (my intention) it merely logged warnings. I changed the SecDefaultAction in vim /etc/httpd/modsecurity.d/modsecurity_crs_10_config.conf from