collects and processes NetFlow data

 Flow-tools is library and a collection of programs used to collect,
 send, process, and generate reports from NetFlow data. The tools can be
 used together on a single server or distributed to multiple servers for
 large deployments. The flow-tools library provides an API for
 development of custom applications for NetFlow export versions 1,5,6 and
 the 14 currently defined version 8 subversions. A Perl and Python
 interface have been contributed and are included in the package.
 .
 A NetFlow is network traffic information exported (via UDP) to an external
 machine. The external machine processes such information to produce network
 traffic accounting, network billing, network monitoring, etc.