[Snort-users] reputation preprocessor and IDS

waldo kitty wkitty42 at ...14940...
Tue Jun 4 21:14:23 EDT 2013


On 6/4/2013 18:20, Joel Esler wrote:
> On Jun 4, 2013, at 4:04 PM, waldo kitty <wkitty42 at ...14940...> wrote:
>> i'll have to dig and see if there is/was a bug that was fixed from 2.9.4.1
>> to the latest snort versions... i whitelisted a CIDR block and they still
>> generate alerts... specifically, we saw alerts on 129:20 when snort was
>> reloading after setting the CIDR block in the whitelist file and bouncing
>> snort with a complete exit and startup... we've also seen 128:4 when
>> sshing into that sensor on a non-standard port but we DO have that
>> non-standard port listed in the ssh config section of snort.conf... these
>> alerts happen for only a short time and then snort seems to settle down and
>> stop issuing them even though those same connections are still active or
>> being terminated and restarted again...
>
> Whitelist doesn't mean "totally ignore these hosts", whitelist is used in
> the term of "these things in this whitelist? yeah, they /never/ get
> blacklisted"

that makes a difference... but how does it truly affect things in IDS mode? i 
can see how it affects things in IPS mode where snort has to allow or disallow 
the passage of the data packets but in IDS mode snort is passive as far as the 
traffic flowing thru... other than raising an alert... isn't it?? so it would 
seem that a whitelist entry would tell snort to not alert on that IP...

> If you want to ignore a host, bpf it out like normal.

ahhh... yeah... bpf is not part of our distributed methodology... it adds too 
much more to go wrong because someone didn't understand thing properly... 
normally i'd just threshold the IP so that it passes everything... i think 
that's how it has been done in the past isn't it?

in any case, it is one of our users that was trying this method so as to prevent 
alerts from even happening on the named IP... i'm just following up on the whys 
and wherefores as to why it did not work the way they (and many of us) thought 
it did...

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