nfdump - Netflow processing tools

nfdump is a set of tools to collect and process netflow data. It's
fast and has a powerful filter pcap like syntax. It supports netflow
versions v1, v5, v7, v9 and IPFIX as well as a limited set of sflow
and is IPv6 compatible.

For CISCO ASA devices, which export Netflow Security Event Logging
(NSEL) records, please use nfdump-1.5.8-2-NSEL.