Snort is a free lightweight network intrusion detection system for both UNIX and Windows.
In this article, let us review how to install snort from source, write rules, and perform basic testing.
1. Download and Extract Snort
Download the latest snort free version from snort website. Extract the snort source code to the /usr/src directory as shown below.
# cd /usr/src # wget -O snort-2.8.6.1.tar.gz http://www.snort.org/downloads/116 # tar xvzf snort-2.8.6.1.tar.gz
Note: We also discussed earlier about Tripwire (Linux host based intrusion detection system) and Fail2ban (Intrusion prevention framework)
2. Install Snort
Before installing snort, make sure you have dev packages of libpcap and libpcre.
# apt-cache policy libpcap0.8-dev libpcap0.8-dev: Installed: 1.0.0-2ubuntu1 Candidate: 1.0.0-2ubuntu1 # apt-cache policy libpcre3-dev libpcre3-dev: Installed: 7.8-3 Candidate: 7.8-3
Follow the steps below to install snort.
# cd snort-2.8.6.1 # ./configure # make # make install
3. Verify the Snort Installation
Verify the installation as shown below.
# snort --version
,,_ -*> 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: 7.8 2008-09-05
4. Create the required files and directory
You have to create the configuration file, rule file and the log directory.
Create the following directories:
# mkdir /etc/snort # mkdir /etc/snort/rules # mkdir /var/log/snort
Create the following snort.conf and icmp.rules files:
# cat /etc/snort/snort.conf include /etc/snort/rules/icmp.rules # cat /etc/snort/rules/icmp.rules alert icmp any any -> any any (msg:"ICMP Packet"; sid:477; rev:3;)
The above basic rule does alerting when there is an ICMP packet (ping).
Following is the structure of the alert:
<Rule Actions> <Protocol> <Source IP Address> <Source Port> <Direction Operator> <Destination IP Address> <Destination > (rule options)
| Structure | Example |
|---|---|
| Rule Actions | alert |
| Protocol | icmp |
| Source IP Address | any |
| Source Port | any |
| Direction Operator | -> |
| Destination IP Address | any |
| Destination Port | any |
| (rule options) | (msg:”ICMP Packet”; sid:477; rev:3;) |
5. Execute snort
Execute snort from command line, as mentioned below.
# snort -c /etc/snort/snort.conf -l /var/log/snort/
Try pinging some IP from your machine, to check our ping rule. Following is the example of a snort alert for this ICMP rule.
# head /var/log/snort/alert [**] [1:477:3] ICMP Packet [**] [Priority: 0] 07/27-20:41:57.230345 > l/l len: 0 l/l type: 0x200 0:0:0:0:0:0 pkt type:0x4 proto: 0x800 len:0x64 209.85.231.102 -> 209.85.231.104 ICMP TTL:64 TOS:0x0 ID:0 IpLen:20 DgmLen:84 DF Type:8 Code:0 ID:24905 Seq:1 ECHO
Alert Explanation
A couple of lines are added for each alert, which includes the following:
- Message is printed in the first line.
- Source IP
- Destination IP
- Type of packet, and header information.
If you have a different interface for the network connection, then use -dev -i option. In this example my network interface is ppp0.
# snort -dev -i ppp0 -c /etc/snort/snort.conf -l /var/log/snort/
Execute snort as Daemon
Add -D option to run snort as a daemon.
# snort -D -c /etc/snort/snort.conf -l /var/log/snort/
Additional Snort information
- Default config file will be available at snort-2.8.6.1/etc/snort.conf
- Default rules can be downloaded from: http://www.snort.org/snort-rules
My name is Ramesh Natarajan. I will be posting instruction guides, how-to, troubleshooting tips and tricks on Linux, database, hardware, security and web. My focus is to write articles that will either teach you or help you resolve a problem. Read more about
Comments on this entry are closed.
good tutorial for keeping a track of the foreign activities on internet facing systems.
Thanks reamsh.I will definately give it a try to understand that
snort -dev -i ppp0 -c /etc/snort/snort.conf -l /var/log/snort/
and error is :
ERROR: Unable to open rules file “/etc/snort//etc/snort/rules/local.rules”: No such file or directory.
Distro i use Fedora 13 .
In the first step you have us download the compressed file, then navigate to another directory to open. Shouldn’t you have us move the file to the other directory first? Either way it doesn’t work. If I try to unpack the compressed file from the usr/src directory it isn’t found (because we didn’t move it), and if I move the file to that directory and try it, I get a series of fails at unpacking.
A little help?
Can I use snort to monitor my webapp’s logs like Python / Java ??
karthik, you can use OSSEC (http://www.ossec.net) to monitor web server logs
To Catalin:
First of all create your /etc/snort/rules/icmp.rules
Then modify /etc/snort/snort.conf in the following way:
# cat /etc/snort/snort.conf
include rules/icmp.rules
I think here is a more better solution and it works grt…!
why command snort not found after installing snort…???
i have been trying for so many days and the when i type snort –version its says command snort not found… please help me to resolve this
Aritcle is very nice.
However can you please also tell me how do i set snort to send alert to external mail id.
when I run snort there is error like this:
“Unable to open rules file: /etc/snort/../rules/local.rules ”
can you help me?
thanks!
Thanks, this tutorial is still working for the newest snort version 2.9.6.0
Thank you very much for the easy installation tutorial.
Had one or two bumps (installing it on ubuntu server 12.04)
I had to install the following packets:
flex, bison and daq(can be found on snort webpage),
Flex and bison could be installed using apt-get install.
Cheers.
If we add snort as demon, snort will startup automatically when the pc is on. right? If so how can i remove from starup demon?
Hi Everyone,
i am having difficulty with snort installation. snort installation keeps giving me same error again and again for different versions of snort.
Error
ERROR! daq_static library not found, go get it from
can anyone help to figure out the issue ?
i would be grateful for the help.
thanks
thanks, i installed snort and added the rule. But when i try to ping another machine i dont get any alert. any idea why ?
can anyone help me to configure snort at the first time because am using opensuse12 ,so when i tried to install snort there is a message that asking me to put dependances first of all,can someone plz help this?
when i tape this commande snort -c /etc/snort/snort.conf -l /var/log/snort/ poster this commenter Commencing packet processing (pid=3220)
What is the problem
Just a Question
I know this may sound stupid, however is there any advantage to using snort over just an IPTABLES rule if all you’re doing is logging the activity? Does snort offer any other notification capabilities, such as e-mail or storing alerts in a database?