"Community ID" flow hashing for Bro

This Bro package provides support for "community ID" flow hashing, a standardized way of labeling traffic flows in network monitors. When loaded, the package adds a community_id string field to conn.log. This is work in progress between the Bro and Suricata communities, to enable correlation of flows in the outputs of both tools. Feedback is very welcome, also from users/developers of other monitoring software.

This package implements a BiF to implement the hashing logic and thus needs binary compilation, so it's also a Bro plugin. Here's an example of a resulting conn.log:

#separator \x09
#set_separator  ,
#empty_field    (empty)
#unset_field    -
#path   conn
#open   2018-01-31-13-06-56
#fields ts      uid     id.orig_h       id.orig_p       id.resp_h       id.resp_p       proto   service duration        orig_bytes      resp_bytes      conn_state      local_orig      local_resp      missed_bytes    history orig_pkts       orig_ip_bytes   resp_pkts       resp_ip_bytes   tunnel_parents  community_id
#types  time    string  addr    port    addr    port    enum    string  interval        count   count   string  bool    bool    count   string  count   count   count   count   set[string]     string
1071580904.891921       CPcWB54kqKkvkdNEXe 34855   80      tcp     -       0.311104        496     1731    SF      -       -       2227    ShADadfF        6       816     6       2051    -       1:LQU9qZlK+B5F3KDmev6m5PMibrg=
#close  2018-01-31-13-06-56

Protocol support

The Community ID spec currently envisions support for a number of protocol constellations for which Bro does not track flow-level state because its analyzers wouldn't know what to do with the traffic. For such flows Bro never triggers the connection-related events used by the package, so there won't be output in conn.log anyway. (If there were protocols Bro tracks at the flow level but the plugin doesn't support, the reported ID would be empty.) We currently support TCP and UDP over IPv4 or IPv6, as well as ICMPv4 and ICMPv6. We do not support other transport-level protocols (such as SCTP), or general IP-address-pair flows for unsupported transport layer protocols.

Using the package

The package's name is bro-community-id; the plugin's name is Corelight::CommunityID. You can see the package's configuration options in the corresponding Bro policy.


The package includes btests that verify plugin loading and crunch included test pcaps through Bro to check baselined Bro console output.


For questions and feedback, please get in touch on the Bro mailing list, or contact Christian Kreibich (

Package Version :