[Bro] unmatched_HTTP_reply in weird.log

Justin Azoff JAzoff at albany.edu
Thu Jul 24 12:09:17 PDT 2014

On Thu, Jul 24, 2014 at 01:51:05PM -0500, Gary Faulkner wrote:
> Hello,
> Recently my Bro cluster started producing a lot of unmatched_HTTP_reply 
> messages in weird.log and seemed to also stop logging outbound GET 
> requests in http.log. I did some testing by following both Bro logs as I 
> browsed to various websites and it looks like every time I visit a new 
> site, the initial GET request doesn't get logged and a weird is 
> generated. As such I'm wondering if this may be an indication that Bro 
> is only seeing half the conversation? I can trace the change in logging 
> behavior to a specific day, but I can't find any indication that there 
> were any changes locally that would have stopped Bro from seeing any 
> particular traffic. Anyone thoughts? Am I interpreting the logs correctly?
> Regards,
> Gary

Most likely this is a problem upstream from Bro.

To rule out bro as a problem here do something like

    tcpdump -nn -i eth1 host your.ip.address and port 80

if you only see one side of the conversion in tcpdump as well that will
rule bro out as the problem.

-- Justin Azoff

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