Re: Tagged Packet

[Joel Esler <joel.esler () sourcefire com>]

The recommendation to disable stream4 is very bad :)

Stream4 is not in charge of fragmentation, frag3 is.  Stream4 does  
tcp conversation reconstruction.  If you disable Stream4 you will  
render ALOT of rules totally null and void.

Joel


On Jan 22, 2006, at 6:05 AM, Dirk Geschke wrote:

> Hi Marco,
>
> > > stream4 can reassemble tcp streams. If an alert is
> > > triggered by
> > > this packet than the unified output plugin will
> > > decompose this
> > > packet to the original smaller ones.
> > >
> > > The alert is associated with the first packet, all
> > > further packets
> > > are marked as tagged packets.
> >
> > Thanks for the explaination.
> > So, what must i do to never get this tagged packet alerts?
>
> oh, there are many options (I think you have no rules with
> the tag keyword.)
>
>   + disable strem4 which reassembles tcp packets. But this is not
>     a good idea since you will be blind against fragmented attacks.
>
>   + do not use the unified output plugin, this is the location
>     where the reassembled tcp packet is split into tagged once
>
>   + edit the unified output plugin to log the full reassembled
>     packet as it was with earlier versions of snort...
>
> Best regards
>
> Dirk
>
>
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