This script is able to parse incoming UDP NetFlow packets of NetFlow version 9.

Version 9 is the first NetFlow version using templates. Templates make dynamically sized and configured NetFlow data flowsets possible, which makes the collector's job harder.

Copyright 2017, 2018 Dominik Pataky dev@bitkeks.eu

Licensed under MIT License. See LICENSE.

In this repo you also find main.py and analyze_json.py.

To start an example collector run python3 main.py -p 9000 -D. This will run a collector at port 9000 in debug mode. Point your flow exporter to this port on your host and after some time the first ExportPackets should appear (the flows need to expire first).

After you collected some data, main.py exports them into JSON files, simply named <timestamp>.json.

To analyze the saved traffic, run analyze_json.py <json file>. In my example script this will look like the following, with resolved hostnames and services, transfered bytes and connection duration:

2017-10-28 23:17.01: SSH     | 4.25M    | 15:27 min | localmachine-2 (<IPv4>) to localmachine-1 (<IPv4>)
2017-10-28 23:17.01: SSH     | 4.29M    | 16:22 min | remotemachine (<IPv4>) to localmachine-2 (<IPv4>)
2017-10-28 23:19.01: HTTP    | 22.79M   | 47:32 min | uwstream3.somafm.com (173.239.76.148) to localmachine-1 (<IPv4>)
2017-10-28 23:22.01: HTTPS   | 1.21M    | 3 sec     | fra16s12-in-x0e.1e100.net (2a00:1450:4001:818::200e) to localmachine-1 (<IPv6>)
2017-10-28 23:23.01: SSH     | 93.79M   | 21 sec    | remotemachine (<IPv4>) to localmachine-2 (<IPv4>)
2017-10-28 23:51.01: SSH     | 14.08M   | 1:23.09 hours | remotemachine (<IPv4>) to localmachine-2 (<IPv4>)

Feel free to customize the analyzing script, e.g. make it print some nice graphs or calculate broader statistics.

• Cisco NetFlow v9 paper
• RFC "Cisco Systems NetFlow Services Export Version 9"

I have specifically written this script in combination with NetFlow exports from softflowd v0.9.9 - it should work with every correct NetFlow v9 implementation though.