Re: Only TCP packets towards the Snort host trigger alerts

[Doug Burks <doug.burks () gmail com>]

Hi Marc,

I think it depends on the network card.  Ubuntu 10.04 was enabling
offloading features for some NICs:
http://securityonion.blogspot.com/2011/10/when-is-full-packet-capture-not-full.html

Doug


On Tue, Nov 13, 2012 at 10:37 AM, Rennhard Marc (rema) <rema () zhaw ch> wrote:

> This solved it, thanks.
>
> It worked without this option with Snort 2.8.5 / Ubuntu 11.04 - it appears
> Ubuntu has recently enabled checksum offloading.
>
> Cheers,
> Marc
>
> On 13. Nov 2012, at 16:08, JJC <cummingsj () gmail com>
>  wrote:
>
> > Out of curiosity, are you running with -k none ?
> >
> >
> > On Tue, Nov 13, 2012 at 7:00 AM, Rennhard Marc (rema) <rema () zhaw ch>
> wrote:
> > Dear list members
> >
> > I'm using Snort for teaching purposes and just updated to Ubuntu 12.04,
> which implied a Snort update from 2.8.5 to 2.9.2.
> > The new version shows a different behaviour with respect to TCP packet
> alerting. Using the rule
> > alert tcp any any -> any any (msg:"ALL"; sid:9999999;)
> >
> > and communicating over TCP to a service running on the same host as
> Snort shows (alerted on) all packets in both directions with Snort 2.8.5.
>  But with the new Snort version (2.9.2), only packets towards the server
> generate an alert. With UPD traffic, all packets are alerted on in both
> directions with both versions.
> > Has anything changed with respect to alerting on TCP packets between
> these two versions?
> > Thanks for any help,
> > Marc
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> Prof. Dr. Marc Rennhard
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>
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-- 
Doug Burks
http://securityonion.blogspot.com

------------------------------------------------------------------------------
Monitor your physical, virtual and cloud infrastructure from a single
web console. Get in-depth insight into apps, servers, databases, vmware,
SAP, cloud infrastructure, etc. Download 30-day Free Trial.
Pricing starts from $795 for 25 servers or applications!
http://p.sf.net/sfu/zoho_dev2dev_nov

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