[Snort-users] Snort 2.9.6.2 inline mode problem

Y M snort at ...15979...
Mon Aug 25 13:18:36 EDT 2014


Please post your snort.conf, sanitizing any private info. Also the command you use to run Snort.
YM

Date: Sun, 24 Aug 2014 19:58:22 +0200
Subject: Re: [Snort-users] Snort 2.9.6.2 inline mode problem
From: demonsdebason at ...11827...
To: snort at ...15979...
CC: snort-users at lists.sourceforge.net

I have already tried with this rule:
drop icmp 192.168.1.2 any -> 8.8.8.8 any (msg: "NEW TEST"; sid:10666;)

Also modified 384 ICMP rule:
drop icmp $EXTERNAL_NET any -> $HOME_NET any (msg:"PROTOCOL-ICMP PING"; icode:0; itype:8; metadata:ruleset community; classtype:misc-activity; sid:384; rev:8;)


Set HOME_NET to any, restarted Snort and got the same crap:
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
>From 8.8.8.8 icmp_seq=1 Destination Port Unreachable
64 bytes from 8.8.8.8: icmp_seq=1 ttl=46 time=40.6 ms

>From 8.8.8.8 icmp_seq=2 Destination Port Unreachable
>From 8.8.8.8 icmp_seq=3 Destination Port Unreachable
64 bytes from 8.8.8.8: icmp_seq=3 ttl=46 time=40.7 ms

I've set additional rule:

drop icmp any any -> any any (msg: "NEW TEST"; sid:10666;)

...and am getting:
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
>From 8.8.8.8 icmp_seq=1 Destination Port Unreachable
64 bytes from 8.8.8.8: icmp_seq=1 ttl=46 time=40.2 ms

>From 8.8.8.8 icmp_seq=2 Destination Port Unreachable
>From 8.8.8.8 icmp_seq=3 Destination Port Unreachable
>From 8.8.8.8 icmp_seq=4 Destination Port Unreachable
>From 8.8.8.8 icmp_seq=5 Destination Port Unreachable

64 bytes from 8.8.8.8: icmp_seq=5 ttl=46 time=40.6 ms
>From 8.8.8.8 icmp_seq=6 Destination Port Unreachable

Tried with and without normalization, works the same.


Snort is blocking, but seems not to be able to drop all the traffic:
08/24-19:56:03.511103  [Drop] [**] [1:10666:0] NEW TEST [**] [Priority: 0] {ICMP} 192.168.1.2 -> 8.8.8.8
08/24-19:56:03.511145  [Drop] [**] [1:10666:0] NEW TEST [**] [Priority: 0] {ICMP} x.x.x.x -> 8.8.8.8

08/24-19:56:03.551092  [Drop] [**] [1:10666:0] NEW TEST [**] [Priority: 0] {ICMP} 8.8.8.8 -> 192.168.1.2
08/24-19:56:03.551058  [Drop] [**] [1:10666:0] NEW TEST [**] [Priority: 0] {ICMP} 8.8.8.8 -> x.x.x.x




On Sun, Aug 24, 2014 at 6:29 PM, Y M <snort at ...15979...> wrote:





Ok, assuming you are setup this way:
Internet <---> eth2 | IPS | eth1 <---> local, where eth1 and eth2 are the listening (promiscuous) interfaces and through which traffic is passing. When you force Snort into inline mode using afpacket, Snort (logically) bridges the interfaces together to let the traffic pass, otherwise drop it when matches occur. Looking again at the rule you have, both destinations are local. What happens if you change both destinations (HOME_NET and EXTERNAL_NET) to any/any? Better, take rule sid:384 and modify it and try to ping an external source and see what happens. For troubleshooting purposes only, run Snort with -A console or -A cmg so you can see whats going directly on the console (without -D).

Also, do you have normalization enabled?
YM
Date: Sun, 24 Aug 2014 17:50:27 +0200
Subject: Re: [Snort-users] Snort 2.9.6.2 inline mode problem
From: demonsdebason at ...11827...

To: snort at ...15979...
CC: snort-users at lists.sourceforge.net


Here is the setup:

INTERNET <--> | IPS/router | <--> | local machines |

IPS box has 4 interfaces, where 2 have an address, others don't. It seemed illogical to set Snort to listen on interfaces where no traffic is passing through.


When I set Snort it to use unaddressed interfaces, nothing happens meaning no alerts are recorded and ICMP echo test isn't working.
Tried setting up bride interfaces and assigning the two unaddressed interface to Snort, same results.


The only results I get is having Snort listening the interfaces traffic traverse though.


On Sun, Aug 24, 2014 at 4:24 PM, Y M <snort at ...15979...> wrote:





How are you testing/connecting the client (icmp echo request sender), the sensor, and the receiver of the icmp? The NICs that Snort is using to receive --> pass/drop --> forward traffic should be inline with no IP addresses. 


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