If you've ever used a freshly installed Ubuntu Server (since 14.x), you definetly noticed the login banner that shows information scraped from the web. This might be Ubuntu news, updates or some other stuff.
From my perspective this is a security risk because every time you log into your server, a request will go to canonical. If you don't know why this might be bad, I suggest that you read this article about HTTP headers and this article on MITM.
You came for a HowTo, here you go:
rm /etc/update-motd.d/10-help-text /etc/update-motd.d/50-motd-news
That's it. No more requests to canonical on login.
You can even go further and edit the
/etc/update-motd.d/00-header script or add your own (the numbers resemble execution queue).
There is one other file in this directory:
/etc/update-motd.d/91-release-upgrade. This script will notify you when updates are available. This also posts requests to canonical but seems more useful than plain news. It's also not that vulnerable to MITM.
Hope that info helped you, I searched for about half an hour to find this.