How to analyze Netflow?

Question

NetFlow

Hello dear!
I distribute the Internet to several people using NAT on a regular Mikrotik. And in the light of political arbitrariness in the country, I am afraid that they may come to me with accusations of some, for example, a bad comment on Vkontakte, although I did not leave it, but my "client" did it.
Therefore, the question is number one: how to track exactly who from the internal local network left a comment on such and such a day, at such and such a second many years ago.
The first thing that comes to my mind is to store Netflow records. That is, by raising the flows during this time, I will see which local IP accessed the external IPs of the VK at that time. Correct me if I'm wrong.
Hooked on this idea, I successfully configured Netflow IPFIX on Mikrotik, installed nfdump on a server with Ubuntu and now I have a lot of files with binary data. But for their simple analysis, I can’t find a tool in any way. And that's question number two.
If I am right in the first part of my question, then please tell me some analyzer or Netflow collector / analyzer with a web interface for Linux for a simple and understandable search for user requests. Well, or any other way of visual representation of data not through the CLI.

Answer 1

you can simply put billing, micro-billing (not advertising, therefore no links). up to 10 free.
there is both a netflow collector and an interface for analysis. There is a nuance, is it true, are you going to perform the spring season? It is necessary to store not only statistics but the data themselves now.

Answer 2

NFA - inexpensive, with a beautiful muzzle.