Installation of OSSEC involves some compiling, so you need gcc and make installed.

You can install both by installing a single package called build-essential.

You also need to install a package called inotify-tools, which is required for real-time alerting to work.

sudo aptitude update
sudo aptitude install build-essential inotify-tools

If database support is needed mysql-dev or postgresql-dev should be installed.

Run the following command to install these packages.

# apt-get install mysql-dev postgresql-dev

http://ossec.github.io/downloads.html

http://documentation.wazuh.com/en/latest/

https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-ossec-security-notifications-on-ubuntu-14-04