Pop along to the Snort Site for the downloads.
I would not recomend installing this as your live version, but advise you to give it a go.
New additions in this version :-
- Target-based stream reassembly, including handling of TCP data overlaps and anomalous TCP header flags on a per-destination basis. 11 different target-based policies are supported. See README.stream5 for specific configuration options for operating system targets.
- UDP session tracking
- Option to emulate Stream4 flushing behaviour
- Stream5 replaces BOTH Stream4 Flow — should disable both of these when Stream5 is enabled.