I'd like to know if I can further secure an AWS EC2 stack (in addition to the .pem file and the allowed SSH inbound ip address security-group)
by requiring that an sms authentication code be entered into the terminal in addition to the .pem file from the terminal.
The cell phone that gets the SMS would be my cell phone, therefore no one would be able to SSH in without me knowing.
unless.. someone changed the SMS number to send the code to their own cell phone... but that person would also need the .pem file and and whatever credentials would be required to change the SMS'd phone #.