Security considerations when running a VM

Parent page: Cloud

On the cloud, you are responsible for the security of your virtual machines.

This document is not a complete guide, but will set out some things you need to consider when creating a VM on the cloud. Links to some different parts of the video:

• Talk overview

Basic security talk recording

There is a recording of an ~1 hr talk on some basic security considerations when working with VMs in the cloud available on youtube called Safety First!. A list of links to different sections of the recording:

• Talk overview
• Cloud service levels
• General security principles
• Key topics
• Creating a first VM (with some comments about security)
• OpenStack security groups
• SSH Security
• Logs
• Creating backups of VMs

Keep the operating system secured

• Apply security updates on a regular basis (see updating your VM).
• Avoid using packages from unknown sources.
• Use a recent image; for example, don't use Ubuntu 14.04 when Ubuntu 18.04 is available.
• Use SSH key authentication instead of passwords. Cloud instances use SSH key authentication by default, and enabling password-based authentication is significantly less secure.
• Install fail2ban to block brute-force attacks.

Network security

• Limit who can access your service. Avoid using 0.0.0.0 in the CIDR field of the security group form - in particular, don't create rules for "0.0.0.0" in the default security group, which applies automatically to all project instances.
  • Be aware of the range you are opening with the netmask your are configuring.
• Do not bundle ranges of ports to allow access.
• Think carefully about your security rules. Consider the following:
  • These services aren't meant to be publicly accessible:
    • ssh (22) - this service allows interactive login to your instance and MUST NOT be made publicly accessible
    • RDP (3389) - this service allows interactive login to your instance and MUST NOT be made publicly accessible
    • mysql (3306)
    • postgresql (5432)
    • nosql
    • tomcat
    • ... many, many others
  • Some services are meant to be accessible from the internet:
    • Apache (80, 443)
    • Nginx (80, 443)
    • ... others
• Configure your web server to use HTTPS instead of HTTP.
  • In many case HTTP should only be used to redirect traffic to HTTPS.
• Do NOT run a mail server.

Updating your VM

In order to keep a VM's operating system secure, it must be regularly updated - ideally weekly, or as often as new packages become available. To upgrade a Linux VM choose the commands below for your particular distribution. Note you will need to reconnect to your VM after rebooting.

Ubuntu/Debian

$ sudo apt-get update
$ sudo apt-get dist-upgrade
$ sudo reboot

CentOS

$ sudo yum update
$ sudo reboot

Fedora

$ sudo dnf update
$ sudo reboot

Further reading

An amazon article on securing instances: https://aws.amazon.com/articles/1233/

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