Zabbix - Track, record, alert and visualize performance and availability of IT resources
Riemann - Container Monitoring
nfsen-ng - nfsen-ng aims to be an in-place replacement for the ageing nfsen.
Wazuh - Open Source Host and Endpoint Security
FastNetMon - FastNetMon is a very fast DDoS analyzer with sflow/netflow/mirror support.
Fortinet FortiAnalyzer - Fortinet FortiAnalyzer is a powerful product for Security Fabric Analytics and Automation.