flowd is a small, fast, secure, and featureful NetFlow
collector. It supports NetFlow versions 1, 5, 7, and 9 over IPv4 and IPv6 transports, IPv6 flows (using NetFlow 9), filtering and tagging of received flows using a packet filter-like language, Perl and Python APIs, flexible storage (with run-time selection of which NetFlow fields are stored), reception of multicast flow datagrams, and privilege separation for security. The flowd distribution also includes a set of supplemental tools including analysis and SQL database support.
