Light-weight system monitor for X
VoIP SIP and SKINNY quality analyzer and packet / audio recording tool
Open Source Monitoring System for performance and availability.
Nagios Open Source network monitoring software - The Standard In ITM
Enhanced Apache Server Status page - for one or multiple servers
Monitoring and reporting web gui for Bacula
Firewall log analyzer
Painel de Monitoramento em PHP/MySQL
free netflow analyzer
A simple, portable port scanner
Enterprise-class, distributed monitoring solution for networks & apps
PHP-based looking glass for Cisco, Juniper & Zebra/Quagga routers
OPTOSS Next Gen Network Management System (NG-NetMS)
Open source tool to monitor your servers and websites
Open Source SIEM
Netflow visualisation and investigation tool