[Bro] [bro] Custom log file

Johanna Amann johanna at icir.org
Tue Apr 25 08:07:53 PDT 2017


On Fri, Apr 21, 2017 at 12:19:51PM -0400, M. Aaron Bossert wrote:
> Sorry, forgot to add the [bro] in the subject line...

It actually is added automatically :)

> > I am using bro 2.5 to process PCAP dumps and am storing both the raw
> > PCAP and the bro logs in Hbase.  I already have an acceptable pipeline
> > for getting both bro logs and PCAP into Hbase, but I want to be able
> > to have each packet linked back to the conn.log entry (using the uid
> > field).

> > Currently, I am doing this in Hbase, but would rather have bro do it
> > for me.  Is it possible to have bro create either individual PCAP
> > files for each log entry or a single log file that listed individual
> > packets (presumably with a packet offset in the PCAP file) along with
> > the uid from the conn.log file?

Let me prefix this with the caveat of "this is probably not a good idea,
because Bro is not built for this use-case". That being said - I don't
think that Bro exposes the packet offset of a pcap file, so that is out.
However, it should indeed be possible to create individual pcap files for
each conn.log entry.

The way I would try doing this is catching the new_packet event
https://www.bro.org/sphinx/scripts/base/bif/event.bif.bro.html#id-new_packet
and then using dump_current_packet to write the packet to a pcap file
https://www.bro.org/sphinx/scripts/base/bif/bro.bif.bro.html#id-dump_current_packet
(dump_current_packet appends to already existing filess).

Note that I did not test if this really works and this probably carries a
hefty performance penalty.

Johanna


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