Just as a reminder for myself (mainly for when I receive a warning by email and don’t remember some of the CLI commands ;-) )
This website DigitalOcean has a very well written, clear tutorial:rkhunter. This software checks your system against a database of known rootkits. Additionally, it can check other system files to make sure they are in line with expected properties and values. In this guide, we will install and configure rkhunter to protect our Ubuntu 12.04 VPS. Continue reading on DigitalOcean
It says Ubuntu 12.04, but I just used it on 14.04. It’s not really an application type to change quickly.
There’s one thing I would add for those who’ve never set up a cronjob using the crontab command. It saves as a temp. file, but will work.