Zabbix - Track, record, alert and visualize performance and availability of IT resources

Zenoss Core - Zenoss (Zenoss Core) is an open source application, server and network management platform based on...

Abusix - Abusix is a network security company that offers email threat protection and network abuse handling solutions to ISPs, Telcos, and Cloud/Hosting Providers to stop the rapidly growing problem of email-borne threats and other kinds of network abuse.

LANState - LANState - Network Mapper and Device Monitor

FastNetMon - FastNetMon is a very fast DDoS analyzer with sflow/netflow/mirror support.

Nagios - Complete monitoring and alerting for servers, switches, applications, and services