SecurityOnion - Security Onion is a free and open source Linux distribution for intrusion detection, enterprise security monitoring, and log management.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
Suricata - Suricata is a high performance Network IDS, IPS and Network Security Monitoring engine.
Prometheus - An open-source systems monitoring and alerting toolkit.
Wazuh - Open Source Host and Endpoint Security