Install ModSecurity with Apache on Ubuntu 22.04

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Welcome to our guide on how to install ModSecurity with Apache on Ubuntu 22.04. Modsecurity is an open source, cross platform web application firewall (WAF) developed by Trustwave’s SpiderLabs. It provides a robust event-based programming language which protects web applications against a wide range of attacks such as SQL injection, Cross-site Scripting (XSS), Local File Include, Remote File Include It also allows for HTTP traffic monitoring, logging and real-time analysis.

There exists two versions of ModSecurity. Modsecurity 2.x and libmodsecurity (Modsecurity 3.x) which is a complete rewrite of Modsecurity 2.

Install ModSecurity with Apache on Ubuntu 22.04

To begin with, re-synchronize your system packages to their latest versions.

apt update

Install Apache Web Server on Ubuntu 22.04

ModSecurity runs on a top of a web server. In this guide, we are using Apache. If not already installed, you can install Apache

Install LAMP Stack on Ubuntu 22.04

You can now choose to install Modsecurity 2 or install Modsecurity 3.

The two work fine. However, I would choose Modsecurity 2.x for due some issues whereby with Modsecurity 3.x, when you enable blocking of detected attacks, the logs are only written to modsec_audit.log file and not to Apache error.log. The choice is yours on which one to install, however.

Install Modsecurity 2.x on Ubuntu 22.04

If you want to install ModSecurity 2 (2.9.5 to be specific), you can run the command below;

apt install libapache2-mod-security2

Install Modsecurity 3.x on Ubuntu 22.04

  • Install Required Build Tools and Dependencies

To install Libmodsecurity or Modsecurity 3 (3.0.6 to be specific) on Ubuntu 22.04, we are going to build it from source. Hence, you need to install some required build tools and dependencies for a successful build.

apt install g++ flex bison curl apache2-dev doxygen \
libyajl-dev ssdeep liblua5.2-dev libgeoip-dev libtool \
dh-autoreconf libcurl4-gnutls-dev libxml2 libpcre++-dev \
libxml2-dev git -y
  • Compile and Install ModSecurity on Ubuntu 22.04

Once your system is setup, you can proceed to install Modsecurity v3 on Ubuntu 22.04.

  • Download ModSecurity Source Code

To install the latest stable version of ModSecurity, you need to compile it from the source.

Therefore, navigate to ModSecurity releases page and download ModSecurity 3 source code. You can simply use wget to pull it.


Extract the ModSecurity source code.

tar xzf modsecurity-v3.0.6.tar.gz
  • Compile and Install ModSecurity 3 on Ubuntu 22.04

Navigate to the ModSecurity source directory, configure, compile and install it

cd modsecurity-v3.0.6

Configure ModSecurity to adapt it to your system and check if any required dependency is missing.


You can safely ignore the fatal: not a git repository (or any of the parent directories): .git error and the obsolete warning messages.


Be sure to fix any dependency issue, if any, before you can proceed to compile and install ModSecurity.

If the configure script above completes with no error, proceed to compile and install LibModSecurity on Ubuntu 22.04.

make install

LibModSecurity aka ModSecurity v3 has now been installed on Ubuntu 22.04

  • Install ModSecurity-Apache Connector

The ModSecurity-apache connector provides a communication channel between Apache and libModsecurity. Now that libmodsecurity is installed, follow through the following steps to install Modsecurity Apache connector.

Clone the git repository for the ModSecurity Apache connector.

cd ~
git clone

Navigate to ModSecurity-apache directory and run the following commands to compile and install it.

cd ModSecurity-apache
./configure --with-libmodsecurity=/usr/local/modsecurity/
make install

Configure Apache with ModSecurity

Configure Modsecurity 2.x

Rename sample configuration;

cp /etc/modsecurity/modsecurity.conf{-recommended,}

Download OWASP ModSecurity Core Rule Set (CRS) into /etc/modsecurity/crs/ directory.

git clone
cp -r owasp-modsecurity-crs/rules /etc/modsecurity/crs/

Configure Apache to load Modsecurity rules;

cp /etc/apache2/mods-available/security2.conf{,.old}

cat > /etc/apache2/mods-available/security2.conf << 'EOL'
<IfModule security2_module>
        SecDataDir /var/cache/modsecurity
        Include /etc/modsecurity/modsecurity.conf
        Include /etc/modsecurity/crs/crs-setup.conf
        Include /etc/modsecurity/crs/rules/*.conf

Enable Modsecurity OWASP rules blocking;

vim /etc/modsecurity/crs/crs-setup.conf

Comment the lines below by adding # at the beginning of a line;

SecDefaultAction "phase:1,log,auditlog,pass"
SecDefaultAction "phase:2,log,auditlog,pass"

Such that they look like;

#SecDefaultAction "phase:1,log,auditlog,pass"
#SecDefaultAction "phase:2,log,auditlog,pass"

And then uncomment the lines below by removing the # at the beginning of the line;

# SecDefaultAction "phase:1,log,auditlog,deny,status:403"
# SecDefaultAction "phase:2,log,auditlog,deny,status:403"

Such that they look like;

SecDefaultAction "phase:1,log,auditlog,deny,status:403"
SecDefaultAction "phase:2,log,auditlog,deny,status:403"

Save the changes and exit the file.

Turn on Modsecurity Engine;

sed -i 's/SecRuleEngine DetectionOnly/SecRuleEngine On/' /etc/modsecurity/modsecurity.conf

Configure Modsecurity 3.x

Configure Apache to load Modsecurity Apache connector module by adding the line below to the main Apache configuration file.

echo "LoadModule security3_module /usr/lib/apache2/modules/" | sudo tee -a /etc/apache2/apache2.conf

Create ModSecurity configuration directory under /etc/apache2

sudo mkdir /etc/apache2/modsecurity.d

Copy the sample ModSecurity configuration file from the source code directory to the ModSec configuration directory created above renaming it as follows.

sudo cp ~/modsecurity-v3.0.6/modsecurity.conf-recommended /etc/apache2/modsecurity.d/modsecurity.conf

Also copy the unicode.mapping file from ModSecurity source directory to Apache Modsecurity configuration directory.

sudo cp ~/modsecurity-v3.0.6/unicode.mapping /etc/apache2/modsecurity.d/

Turn on ModSecurity by changing the value of SecRuleEngine to On.

sed -i 's/SecRuleEngine DetectionOnly/SecRuleEngine On/' /etc/apache2/modsecurity.d/modsecurity.conf

Next, you need to configure ModSecurity rules.

Therefore, create a file where you can define the rules to include, say, /etc/apache2/modsecurity.d/modsec_rules.conf.

cat > /etc/apache2/modsecurity.d/modsec_rules.conf << 'EOL'
Include "/etc/apache2/modsecurity.d/modsecurity.conf"
Include "/etc/apache2/modsecurity.d/owasp-crs/crs-setup.conf"
Include "/etc/apache2/modsecurity.d/owasp-crs/rules/*.conf"

Since we have included the OWASP Rules as part of ModSecurity 3 rules, proceed to install them.

The OWASP ModSecurity Core Rule Set (CRS) is a set of generic attack detection rules for use with ModSecurity. It aims at protecting the web applications from a wide range of attacks, including the OWASP Top Ten, minimum of false alerts.

Clone the CRS from GitHub repository to /etc/apache2/modsecurity.d/ as shown below;

git clone /etc/apache2/modsecurity.d/owasp-crs

Next, rename crs-setup.conf.example to crs-setup.conf.

sudo cp /etc/apache2/modsecurity.d/owasp-crs/crs-setup.conf{.example,}

Similarly, enable Modsecurity OWASP rules blocking by editing the /etc/apache2/modsecurity.d/owasp-crs/crs-setup.conf file above;

vim /etc/apache2/modsecurity.d/owasp-crs/crs-setup.conf

#SecDefaultAction "phase:1,log,auditlog,pass"
#SecDefaultAction "phase:2,log,auditlog,pass"

SecDefaultAction "phase:1,log,auditlog,deny,status:403"
SecDefaultAction "phase:2,log,auditlog,deny,status:403"

NOTE that with this change, it causes ModSecurity 3 to log to modsec_audit.log file ONLY and not to Apache error.log.

For ModSecurity 2, the attack logs are written to Apache error log. This makes it easy to process these logs with other external security monitoring tools.

Activate ModSecurity Apache Protection on Ubuntu

After all that, activate the Modsecurity on the default site configuration file or on any virtual host configuration file. In this guide, we are using Apache’s default site configuration file.

Activate Modsecurity 2.x on Ubuntu

If you are running Modsecurity 2.x, all you need to do at this point is to restart Apache web server.

apachectl -t
systemctl restart apache2

Activate Modsecurity 3.x on Ubuntu

If you are running Modsecurity 3.x, activate it as follows;

cp /etc/apache2/sites-available/000-default.conf{,.old}

See our sample default site virtual host configuration with no comments;

cat > /etc/apache2/sites-available/000-default.conf << 'EOL'
<VirtualHost *:80>
	modsecurity on
	modsecurity_rules_file /etc/apache2/modsecurity.d/modsec_rules.conf 
	ServerAdmin webmaster@localhost
	DocumentRoot /var/www/html
	ErrorLog ${APACHE_LOG_DIR}/error.log
	CustomLog ${APACHE_LOG_DIR}/access.log combined

The lines;

	modsecurity on
	modsecurity_rules_file /etc/apache2/modsecurity.d/modsec_rules.conf 

Turns on Modsecurity and specifies the location of the Modsecurity rules.

Check Apache for configuration errors and restart it.

apachectl -t

If there is no error, you should get the output, Syntax OK.

systemctl restart apache2

Testing Modsecurity

Next, test the effectiveness of Modsecurity, for example, command injection. Run the command below;

curl localhost?doc=/bin/ls
<title>403 Forbidden</title>
<p>You don't have permission to access this resource.</p>
<address>Apache/2.4.52 (Ubuntu) Server at localhost Port 80</address>

Check Modsecurity logs;

tail /var/log/modsec_audit.log

ModSecurity: Access denied with code 403 (phase 2). Matched "Operator `PmFromFile' with parameter `' against variable `ARGS:doc' (Value: `/bin/ls' ) [file "/etc/apache2/modsecurity.d/owasp-crs/rules/REQUEST-932-APPLICATION-ATTACK-RCE.conf"] [line "496"] [id "932160"] [rev ""] [msg "Remote Command Execution: Unix Shell Code Found"] [data "Matched Data: bin/ls found within ARGS:doc: /bin/ls"] [severity "2"] [ver "OWASP_CRS/3.2.0"] [maturity "0"] [accuracy "0"] [tag "application-multi"] [tag "language-shell"] [tag "platform-unix"] [tag "attack-rce"] [tag "paranoia-level/1"] [tag "OWASP_CRS"] [tag "OWASP_CRS/WEB_ATTACK/COMMAND_INJECTION"] [tag "WASCTC/WASC-31"] [tag "OWASP_TOP_10/A1"] [tag "PCI/6.5.2"] [hostname ""] [uri "/"] [unique_id "1651339080"] [ref "o1,6v10,7t:urlDecodeUni,t:cmdLine,t:normalizePath,t:lowercase"]




Similarly, install Nikto on Ubuntu and use it to scan the server to test the modsecurity rules;

Install and Use Nikto Web Scanner on Ubuntu

Access the site from browser and test command injection attack,

Install ModSecurity with Apache on Ubuntu 22.04

Tailing the Apache error logs;

tail -f /var/log/apache2/error.log
[Sat Apr 30 23:43:10.888508 2022] [:error] [pid 4504:tid 140113703069248] [client] [client] ModSecurity: Access denied with code 403 (phase 2). Matched phrase "bin/ls" at ARGS:doc. [file "/etc/modsecurity/crs/rules/REQUEST-932-APPLICATION-ATTACK-RCE.conf"] [line "518"] [id "932160"] [msg "Remote Command Execution: Unix Shell Code Found"] [data "Matched Data: bin/ls found within ARGS:doc: /bin/ls"] [severity "CRITICAL"] [ver "OWASP_CRS/3.2.0"] [tag "application-multi"] [tag "language-shell"] [tag "platform-unix"] [tag "attack-rce"] [tag "paranoia-level/1"] [tag "OWASP_CRS"] [tag "OWASP_CRS/WEB_ATTACK/COMMAND_INJECTION"] [tag "WASCTC/WASC-31"] [tag "OWASP_TOP_10/A1"] [tag "PCI/6.5.2"] [hostname "localhost"] [uri "/"] [unique_id "Ym2fXltd6Nody7X50nHgVQAAAAc"]

As a result, this confirms that the Modsecurity is functioning as expected.

That is just about it on our guide on how to install ModSecurity with Apache.




Other Tutorials

Install ModSecurity 3 with Apache in a Docker Container

Intercept Malicious File Upload with ModSecurity and ClamAV


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3 thoughts on “Install ModSecurity with Apache on Ubuntu 22.04”

  1. Fantastic Article.

    In my case to enable mod security2 I had to run

    $ sudo a2enmod security2

    After the command:

    sed -i ‘s/SecRuleEngine DetectionOnly/SecRuleEngine On/’ /etc/modsecurity/modsecurity.conf

  2. maybe worth mentioning under section “Configure Modsecurity 3.x”
    NOTE: This project is not production ready

    This project should be considered under development and not production ready. The functionality is not complete and so should not be used. With Apache HTTP Server, the recommended version of ModSecurity is v2.9.x.


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