[Snort-users] Problem running Snort Inline

Y M snort at ...15979...
Fri Feb 6 09:40:02 EST 2015



From: anshuman at ...16510...
To: snort-users at lists.sourceforge.net
Date: Fri, 6 Feb 2015 12:50:17 +0000
Subject: Re: [Snort-users] Problem running Snort Inline









Hi Yaser,
 
Please see my answers inline.


 
 
Regards,

Anshuman Anil Deshmukh | Sr. IS Analyst - Security

Phone: 91-20-66041700, 91-20-66044700 (Extn. 6114)

Cell: 91-99230-51641

 


From: Y M [mailto:snort at ...15979...]


Sent: Friday, February 6, 2015 1:02 PM

To: Anshuman Anil Deshmukh

Cc: snort-users

Subject: RE: [Snort-users] Problem running Snort Inline


 



Comments inline.

 




From:
anshuman at ...16510...

To: snort-users at lists.sourceforge.net

Date: Thu, 5 Feb 2015 06:40:16 +0000

Subject: [Snort-users] Problem running Snort Inline

Hi,
 
We have issues running Snort inline. This is the exact problem which is mentioned here -
http://www.linuxforums.org/forum/debian-linux/200751-snort-inline.html
 (see log below).
 
We have setup the Snort inline (version 2.9.7.0) which is compiled using switch --enable-sourcefire.

 
## While might not be related, did you also upgrade the DAQ to 2.0.4? This version was released with the release of Snort 2.9.7.0 as I remember.
#Anshuman – I didn’t upgrade to DAQ 2.0.4 when I upgraded to Snort version 2.9.7.0

* You want to update in the future. Again this may be entirely unrelated.

It says “Enabling inline operation” and then switches to IDS mode.

 
## Are you referring to the message that output in Snort's startup messages? If I recall properly, this came up one before and as I remember that this message "can be" ignored given
 that you are actually running Snort inline.
#Anshuman – Yes, I am referring to the output in Snort’s startup messages.
 * Like I said above, this message should not be a problem and it can be ignored as you have proven that your ICMPs are being dropped (blocked).

Our command line for running Snort:
/usr/local/snort/bin/snort -c /usr/local/snort/etc/snort_conf_rules.conf -i eth0:eth1 -Q --pid-path=/var/run which creates the bridge automatically.
 Both the interfaces doesn’t have IP addresses assigned.
 
## While I have not tested this thoroughly, but does your traffic flows from eth0 --> eth1 or from eth1 --> eth0? If you change -i eth0:eth1 to -i eth1:eth0, what happens? 
#Anshuman – Yes, my traffic flows from eth0
à eth1.

* Try running another simple test for inbound traffic. Just to verify the rule directionality in relation to your HOME/EXTERNAL network configurations works as expected, i.e.: being blocked.
 
We have already enabled following options for snort inline:
config policy_mode:inline
config daq: afpacket
config daq_mode: inline
config daq_var: buffer_size_mb=1024
 
preprocessor normalize_ip4
preprocessor normalize_tcp: ips ecn stream
preprocessor normalize_icmp4
preprocessor normalize_ip6
preprocessor normalize_icmp6
 
Under verdicts it shows 0% packets blocked. We have enabled couple of drop rules for BRUTE FORCE attack one of which is getting detected. Here is the snort output.
02/02-12:12:23.042082  [Drop] [**] [1:2019876:2] ET SCAN SSH BruteForce Tool with fake PUTTY version [**] [Classification: Detection of a Network Scan] [Priority: 3] {TCP} 000.000.000.00:38772 ->
 00.00.00.:22 (IP addresses information removed)
 
## In the above case, was the connection successful? If you try the same using an ICMP rule and pinging some destination, does the ICMP packet go through?.
#Anshuman – In above case I don’t know if connection was successful because the traffic wasn’t generated by me, but it was the real traffic from Internet. If I try the same
 using an ICMP rule and ping a destination, ICMP packet isn’t going through. It gets blocked. My ICMP drop rule is working fine.
 
Here is the section verdict for the session in which I had kept the ICMP rule marked as drop. But you can see that “Block” is still shown as none. Is it like whatever is getting
 blocked is “Blacklist”? * From Snort documentation: "Blacklist = packets that caused Snort to block a flow from passing. This is the case when a block TCP rule fires. If the DAQ supports this in hardware, no further packets will be seen by Snort for that session. If not, snort will block each packet and this count will be higher."

02/06-17:34:48.559180  [Drop] [**] [1:10000001:1] ICMP ping blocked-test rule [**] [Priority: 0] {ICMP} 192.27.6.22 -> 192.168.1.10
 
Verdicts:
      Allow:        20432 ( 45.983%)
      Block:            0 (  0.000%)
    Replace:            0 (  0.000%)
 Whitelist:        23995 ( 54.001%)
  Blacklist:           12 (  0.027%)
     Ignore:            0 (  0.000%)
 
But under verdicts it shows nothing blocked. Why??
 
## Not sure why, but lets verify the above first and then lets see.
 
Verdicts:
      Allow:      4335107 ( 59.187%)
      
Block:            0 (  0.000%)
 
Output says:
Enabling inline operation
Running in IDS mode
 
        --== Initializing Snort ==--
Initializing Output Plugins!
Initializing Preprocessors!
Initializing Plug-ins!
 
===============================================
Information about our setup-
 
   ,,_     -*> Snort! <*-
  o"  )~   Version 2.9.7.0 GRE (Build 149)

   ''''    By Martin Roesch & The Snort Team:
http://www.snort.org/contact#team
           Copyright (C) 2014 Cisco and/or its affiliates. All rights reserved.
           Copyright (C) 1998-2013 Sourcefire, Inc., et al.
           Using libpcap version 1.4.0
           Using PCRE version: 7.8 2008-09-05
           Using ZLIB version: 1.2.3
 
============================================================================
 
/usr/local/snort/bin/snort --daq-list
Available DAQ modules:
pcap(v3): readback live multi unpriv
ipfw(v3): live inline multi unpriv
dump(v2): readback live inline multi unpriv
afpacket(v5): live inline multi unpriv
 
===========================================================================
 
Please let me know in case any other information is required.
 
 
Regards,
Anshuman
 
 

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