[Bro] File extraction exclude local sites

[Mike Kolkebeck]

Does anyone have a solution to exclude extracting files transmitted from
internal hosts?

I modified the script below from the bro exchange exercise, but I continue
to get executable files from internal hosts.  I am using broctl and
networks.cfg is populated.  I haven't tried using the
file_over_new_connection event yet, but I would prefer to use file_new
event, if I can.  Any ideas on what I'm doing wrong?

Thanks!
Mike



global ext_map: table[string] of string = {
    ["application/x-dosexec"] = "exe",
} &default ="";

event file_new(f: fa_file)
    {
    if ( ! f?$mime_type || f$mime_type != "application/x-dosexec" )
        return;

    if ( ! f?$info || ! f$info?$tx_hosts )
        return;

    for ( txhost in f$info$tx_hosts )
        {
        if ( Site::is_local_addr(txhost) )
            return;
        }

    local ext = "";

    if ( f?$mime_type )
        ext = ext_map[f$mime_type];

    local fname = fmt("%s-%s.%s", f$source, f$id, ext);
    Files::add_analyzer(f, Files::ANALYZER_EXTRACT,
[$extract_filename=fname]);
    }
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