[Snort-users] snort inline mode is not working with iptables

Ryan Jordan ryan.jordan at ...1935...
Fri Aug 6 14:58:33 EDT 2010


Congratulations! Everything is working as expected. Pings are ICMP
packets, and judging from your alert file you have successfully
dropped them.

-Ryan

On Fri, Aug 6, 2010 at 2:41 PM, netchild ccie <netchildccie at ...125...> wrote:
> Dear list,
> I a new user to Snort and this is my first experience with.
> My issue is that; it seems the snort does not communicate correctly with
> iptables. I have a linux machine run SNORT 2.8.6 and connected to LAN with
> another linux machine. I am using the other machine to ping the snort
> server. every time I am running snort without iptables, the ping is working
> and once I am using the iptables then launch snort, the ping stopped and
> I received alert messages!!!! I can not understand why snort drop the
> packets?!
>
> I'll try to summarized my issue in points
> 1. I've built linux machine with CentOS 4.8
> 2. I've downloaded snort 2.8.6 from snort website
> 3. I've compiled the package after I installed successfully libipq and
> libnet 1.0.2a. I used the following commands
> ./configure --enable-inline
> make
> make install
> 4. I've built a simple rule under /etc/snort/rules as the below and named
> "local.rule"
> alert icmp any any <> any any (msg: "ICMP DROPPED"; sid: 1000001;)
> 5. I loaded ip_queue model and verify it as below
> [root at ...14955... rules]# modprobe ip_queue
> [root at ...14955... rules]# lsmod | grep queue
> ip_queue               44777  0
> 5. I launched iptables before I started snort as below and verify
> iptables -A OUTPUT -p icmp -j QUEUE
> [root at ...14955... rules]# iptables -L
> Chain INPUT (policy ACCEPT)
> target     prot opt source               destination
> Chain FORWARD (policy ACCEPT)
> target     prot opt source               destination
> Chain OUTPUT (policy ACCEPT)
> target     prot opt source               destination
> QUEUE      icmp --  anywhere             anywhere
> 6. I've run snort as below
> [root at ...14955... rules]# snort -k none -c /etc/snort/snort.conf.wael -l
> /var/log/snort/wael -Q -i eth1
> Enabling inline operation
> Running in IDS mode
>         --== Initializing Snort ==--
> Initializing Output Plugins!
> Initializing Preprocessors!
> Initializing Plug-ins!
> Parsing Rules file "/etc/snort/snort.conf.wael"
> PortVar 'HTTP_PORTS' defined :  [ 80 2301 3128 7777 7779 8000 8008 8028 8080
> 8180 8888 9999 ]
> PortVar 'SHELLCODE_PORTS' defined :  [ 0:79 81:65535 ]
> PortVar 'ORACLE_PORTS' defined :  [ 1521 ]
> .
> .
> .
>         --== Initialization Complete ==--
>    ,,_     -*> Snort! <*-
>   o"  )~   Version 2.8.6.1 (Build 39)
>    ''''    By Martin Roesch & The Snort Team:
> http://www.snort.org/snort/snort-team
>            Copyright (C) 1998-2010 Sourcefire, Inc., et al.
>            Using PCRE version: 6.6 06-Feb-2006
>            Rules Engine: SF_SNORT_DETECTION_ENGINE  Version 1.12  <Build 18>
> 7. Verify through the log
> Aug  6 21:38:45 xen1 snort: [1:1000001:0] ICMP DROPPED {ICMP} 10.6.211.155
> -> 10.6.211.53
> Aug  6 21:39:16 xen1 last message repeated 31 times
> Aug  6 21:40:17 xen1 last message repeated 61 times
>
> 8. verify the ping from the ping's screen
> [root at ...14956... ~]# ping 10.6.211.53
> PING 10.6.211.53 (10.6.211.53) 56(84) bytes of data.
> <nothing>
>
> what I have missed?!
> Regards,
> Wael,
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