Re: False positives(?) for spp_sip

["Pettersson, Emil" <emil.pettersson () sovos com>]

Just to be sure, I found that we have multiples of snort.conf (this is on pfSense I should add), there is I guess the 
“main” one at /usr/local/etc/snort/snort.conf and then there are additional ones for each interface that we have Snort 
enabled on (i.e. /usr/local/etc/snort/snort_2591_em0/snort.conf). The latter seems to overwrite any changes whenever 
the Snort service is restarted so I can’t comment out the SIP pre-processor there, not sure if this is needed or if 
only the former is used to determine what rules are used?

From: Joel Esler (jesler) <jesler () cisco com>
Sent: Friday, 17 April 2020 17:23
To: Pettersson, Emil <emil.pettersson () sovos com>
Cc: snort-sigs () lists snort org
Subject: Re: [Snort-sigs] False positives(?) for spp_sip




On Apr 17, 2020, at 10:23 AM, Pettersson, Emil <emil.pettersson () sovos com<mailto:emil.pettersson () sovos com>> 
wrote:

Thank you Joel, so I would just comment out the entire block below then?


Yes



For reference, do you know if changes such as these would get overwritten during updates? I know we have some 
customization we’ve done for Snort logging (mainly in /usr/local/pkg/snort/snort_check_for_rule_updates.php) and for 
these we end up redoing these changes if Snort package is updated, just wanted to make sure we include in our routines 
if the same goes for the snort.conf file.

snort.conf should be compared every time you update Snort.  Using diff or something similar to make sure we didn’t add 
any additional options, etc.



preprocessor sip: max_sessions 40000, \
   ports { 5060 5061 5600 }, \
   methods { invite \
             cancel \
             ack \
             bye \
             register \
             options \
             refer \
             subscribe \
             update \
             join \
             info \
             message \
             notify \
             benotify \
             do \
             qauth \
             sprack \
             publish \
             service \
             unsubscribe \
             prack }, \
   max_uri_len 512, \
   max_call_id_len 80, \
   max_requestName_len 20, \
   max_from_len 256, \
   max_to_len 256, \
   max_via_len 1024, \
   max_contact_len 512, \
   max_content_len 2048

From: Joel Esler (jesler) <jesler () cisco com<mailto:jesler () cisco com>>
Sent: Friday, 17 April 2020 15:20
To: Pettersson, Emil <emil.pettersson () sovos com<mailto:emil.pettersson () sovos com>>
Cc: snort-sigs () lists snort org<mailto:snort-sigs () lists snort org>
Subject: Re: [Snort-sigs] False positives(?) for spp_sip

Hello Emil,

If you are not running SIP on your network, then yes, comment out the SIP preprocessor and that will solve your 
problem.  This can be done in your snort.conf file.
Sent from my  iPad



On Apr 17, 2020, at 09:01, Pettersson, Emil <emil.pettersson () sovos com<mailto:emil.pettersson () sovos com>> wrote:

Hi,

We’ve been getting a few blocks for traffic from customers, from looking into the logs if I’m understanding correctly 
these are getting caught by spp_sip due to traffic in these instances having source port 5060 (they’re doing a few 
thousand/day with random source port span).
Apr 17 09:33:31 snort[17881]: [140:3:2] (spp_sip) URI is too long [Classification: Potentially Bad Traffic] [Priority: 
2] {TCP} [SOURCE_IP]:5060 -> [DESTINATION_IP]:443
There is no actual SIP traffic expected to go in or out from this network, so regardless of anything else I believe 
there’s no real reason to have these rules enabled? However I am unsure of what the correct way would be to disable 
them?
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