If you want to secure a server, the previously listed measures against external adversities are extremely important. However, it is equally important to ensure that the interaction between hardware and software runs as desired. This is not a one-off check, completed after successfully creating your server environment; this is a long-term task that you should never lose sight of. With the high number of different processes, this is easier said than done, which is why you should have access to help tools from the beginning. These help monitor all the operations on your server and alert any incidents.
An easy program of this kind that is quick to configure is Monit, which can be installed easily on many Linux distributions via the package administrator. The open source application (GNU-AGPL license) selectively monitors processes, files, clouds, hosts, programs, or scripts after starting. The system resources – CPU, memory, and absolute system utilization – can also be monitored. In the Monit configuration file, you can select which values or events generate a notification via e-mail. If you require more information, the monitoring software Nagios is recommended. It is somewhat more complex, but the core version is open source, and can be expanded using diverse plugins. A virtual machine can also allow it to be run on a Windows platform.