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Re: [Snort-users] VRT stream5 Preprocessor Config vs Default Settings
From: Joel Esler <jesler_at_nospam>Date: Fri May 20 2011 - 17:59:05 GMT
To: Joel Esler <jesler@sourcefire.com>
Eoin,
We updated the 2.9.0.5 .conf several weeks ago. These are the defaults that are in it now:
preprocessor stream5_global: track_tcp yes, \
track_udp yes, \
track_icmp no, \
max_tcp 262144, \
max_udp 131072, \
max_active_responses 2, \
min_response_seconds 5
J
On Apr 28, 2011, at 9:31 PM, Joel Esler wrote:
> We've taken this for action on our side. Thanks Eoin.
>
> --
> Sent from my iPad
> Please excuse the brevity
>
> On Apr 28, 2011, at 5:20 PM, Eoin Miller <eoin.miller@trojanedbinaries.com> wrote:
>
>> VRT supplied snort.conf file that comes with 2.9.0.4 as of today contains this line:
>>
>> ---snip---
>> preprocessor stream5_global: max_tcp 8192, track_tcp yes, track_udp yes, track_icmp no max_active_responses 2 min_response_seconds 5
>> ^ ^
>> |---missing commas?----|
>> ---snip---
>>
>> I guess it still loads it with these options? If not it should look like (separated by line to make easier to read in the email threads):
>>
>> preprocessor stream5_global: max_tcp 8192,\
>> track_tcp yes,\
>> track_udp yes,\
>> track_icmp no,\
>> max_active_responses 2,\
>> min_response_seconds 5
>>
>> Some of those settings are even less than what is turned on by default though it would appear. max_tcp is set to 8192 in the VRT conf as shown above, however the 2.9.0.5 manual states:
>> --snip--
>> max_tcp <num sessions> || Maximum simultaneous TCP sessions tracked. The default is ”262144”, maximum is ”1048576”, minimum is ”1”.
>> --snip--
>>
>> What else is weird is that max_udp is missing in the config and therefor the default value of 131072 would kick in, so the VRT config has you tracking a lot more UDP sessions that TCP sessions with stream5. From the 2.9.0.5 manual:
>> --snip--
>> max_udp <num sessions> || Maximum simultaneous UDP sessions tracked. The default is ”131072”, maximum is ”1048576”, minimum is ”1”.
>> --snip--
>>
>> Not sure if this is by design or just an artifact from the previous snort.conf's where this has been set to this value forever in recent memory. Value does seem pretty low however.
>>
>>
>> I guess something more like:
>>
>> preprocessor stream5_global: track_tcp yes,\
>> track_udp yes,\
>> track_icmp no,\
>> max_active_responses 2,\
>> min_response_seconds 5
>>
>> Or:
>>
>> preprocessor stream5_global: track_tcp yes,\
>> max_tcp 262144,\
>> track_udp yes,\
>> max_udp 131072,\
>> track_icmp no,\
>> max_active_responses 2,\
>> min_response_seconds 5
>>
>> Thought this might be worthy of review/consideration for others.
>>
>> -- Eoin
>>
>>
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