The ticket to coordinate on this is  

https://docs.csc.fi/cloud/pouta/security/

Introduction

Security responsibility 

Users are responsible for the security of the virtualized resources under their control. This includes, but it is not limited to: virtual machines, network configuration, user accounts, disk volumes. 

Security reports 

If you discover a critical security flaw or believe that your machine has been compromised, please contact ECMWF or EUM immediately at "usxa@ecmwf.int"

Network 

It is very important to keep your network configuration as secure as possible, as it is the gate any intruder will use to enter in your system. It is relatively simple to apply some good practices that will give a good extra security layer. Here below few strategies are advised.