insightIDR - insightIDR is an incident detection and response tool.
Zabbix - Track, record, alert and visualize performance and availability of IT resources
FireEye Network Security and Forensics - Network Security and Forensics tools help you detect, monitor and respond to complex cyber attacks and zero-day exploits that bypass signature-based defenses.
nfsen-ng - nfsen-ng aims to be an in-place replacement for the ageing nfsen.
Progress WhatsUp Gold - Progress WhatsUp Gold is an all-in-one Network monitoring utility that now offers even more features and functionality to help you monitor your servers, network, and IP address.
FastNetMon - FastNetMon is a very fast DDoS analyzer with sflow/netflow/mirror support.