[Snort-users] Problem running Snort Inline

Y M snort at ...15979...
Fri Feb 6 02:32:25 EST 2015

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

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 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 as I remember.
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.
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
## 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? 
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} ->
 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?.
But under verdicts it shows nothing blocked. Why??
## Not sure why, but lets verify the above first and then lets see.
      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 GRE (Build 149)

   ''''    By Martin Roesch & The Snort 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.

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