Install modsecurity for Apache

ModSecurity is a kind of firewall for Apache, Nginx and IIS. This is a module that provides a set of rules for filtering traffic. This is a ‘must have’ module for any server.

On February 12, 2015 version 2.9.0 was released. It is the most current at the time of this writing.

Even on January 4, 2016, this version is the most current.

We will compile it from source and configure for the Apache web server.

This version requires libxml2 version 2.6.29 to compile properly. The first step is to make sure it is available for your server OS:

yum info libxml2


apt-cache showpkg libxml2

If the required package is available for installation than you can continue.

Make sure you have the following packages installed: RedHat/Centos:

yum install gcc automake libxml2 libxml2-devel httpd-threaded-devel libcurl4-openssl-devel libpcre3-devel


apt-get install gcc automake libxml2 libxml2-dev apache2-threaded-dev libcurl-dev pcre-dev

I will work in the /usr/local/src folder.

cd /usr/local/src

Download the required archive:

wget -no-check-certificate

Unpack and go to the directory:

tar xf modsecurity-2.9.0.tar.gz && cd modsecurity*
make && make install

The module will be installed in the /usr/local/modsecurity/lib folder. The binaries will be in the /usr/local/modsecurity/bin folder.

Next, you need to add the following lines to the Apache configuration file (/etc/httpd/conf/httpd.conf)

LoadModule security2_module /usr/local/modsecurity/lib/

And uncomment:

LoadModule unique_id_module modules/

Next, we take the recommended module configuration and copy it to the Apache conf.d folder:

cp modsecurity.conf-recommended /etc/httpd/conf.d/modsecurity.conf

You can open this file and edit the path to the audit log - SecAuditLog.

When checking the configuration, it may give the following error:

Syntax error on line 212 of /etc/httpd/conf.d/modsecurity.conf:
Could not open unicode map file `/etc/httpd/conf.d/unicode.mapping`: No such file or directory

To fix, copy the desired file:

cp unicode.mapping /etc/httpd/conf.d/

That’s all. Installation completed. Even with the basic set of parameters, the server began to breathe more freely.

To hide the Apache version, disable the Trace method, you can add the following lines to /etc/httpd/conf.d/modsecurity.conf:

ServerSignature Off
Trace Enable Off

More information about all configuration options can be found here

Because mod_security is a firewall, there are rulesets for it that need to be enabled in order for mod_security to be useful.

The list of free rules is available on GitHub:

We download and unpack it:


We create a folder in which we will add the configs for the rules that we need to enable and copy the sets of rules we need:

mkdir /etc/modsecurity/activated_rules
cp owasp-modsecurity-crs-master/base_rules/* /etc/modsecurity/activated_rules/

The following rule sets have done more harm than good, so it’s best to turn them off:

rm /etc/modsecurity/activated_rules/modsecurity_crs_35_bad_robots.conf
rm /etc/modsecurity/activated_rules/modsecurity_crs_41_sql_injection_attacks.conf
rm /etc/modsecurity/activated_rules/modsecurity_crs_21_protocol_anomalies.conf

The following folder deserves additional attention, as it contains recommended rules for popular CMS systems:


Copy the files you need with the extensions .conf and .data to the folder /etc/modsecurity/activated_rules/

Edit the /etc/httpd/conf.d/modsecurity.conf file with the following line to make it work:

Include /etc/modsecurity/activated_rules/*.conf