Updates the Emerging Threats open ruleset for Suricata. Fuuure versions may work with the ET Pro ruleset as well.
$ sudo git clone https://github.com/seanthegeek/etupdate.git
$ sudo cp etupdate/etupdate /usr/sbin
$ sudo /usr/sbin/etupdate.py -V
Edit the crontab:
$ sudo crontab -e
Add the line:
42 * * * * /usr/sbin/etupdate
This will run etupdate every 42 minutes after each hour. You should probably change 42 to some other minute, so everyone following this tutorial doesn't query Emerging Threats for updates at the exact same time.