recently we have noticed of several cases of compromised servers, which are running under Windows Server 2008 R2. These compromised servers reported the excessive CPU usage and it is almost impossible to log in remote desktop through the RDP due to this CPU performance.
If you want to prevent of these complications, please, make sure your operating firewall is set correctly, automatic updates are enabled and your server is upgraded.
We haven´t found any complications in other versions of Windows Server.
Thank you for your cooperation.