Using linux (Ubuntu) instances on Amazon EC2 is a quite safe thing to do, at least measured by the security provided by the platform (security groups, ACL, physical security,..). I recommend reading their security site here. At the end of the day the server is only as secure as you configure it, if you choose to open all ports running services with their default configurations and password settings, Amazon can’t help you.
When connecting to a Ubuntu server with ssh you need to provide the keyfile (somekeyfile.pem) that you can download when creating the key pair.
This 2048 bit key is required to login as regular ubuntu user. What I dislike is the fact that this user can sudo all, so once someone manage to get into you user account, he has root access too. I recommend to set a password for the ubuntu user and change the sudoers configuration.
Change the password for user ubuntu
Open the sudoers include file
sudo vi /etc/suderos.d/90-cloudimg-ubuntu or sudo vi /etc/sudoers
I believe it makes no sense to buy a ~ 900.- SGD (3g, GPS), respectively a 500.- SGD (wifi only) device running Android 2.2 without any chance even to update to 2.3, such as the Galaxy Tab, the same time Galaxy is releasing already the new 3.0 based models. So how to find a cheap device that can compete with the Galaxy Tab ?
After buying one Android 10″ Tablet from DHGate.com without problems I decided to look for a second one, a 7″ device. Certainly not easy to find a good device among the many offers on the trading platform, but I was lucky enough to choose this PC-7006 1Ghz device for 223.- U$ (incl. shipping) from the dealer avatar2012: