Output options for Snort data

Output modes are the methods by which Snort reports its findings when run in IDS mode. As discussed in the first Snort Report, Snort can also run in sniffer and packet logger modes.

    Requires Free Membership to View

In sniffer mode, Snort writes traffic directly to the console. As a packet logger, Snort writes packets to disk in Libpcap format. This article describes output options for IDS mode, called via the -c [snort.conf] switch. Only IDS mode offers output options.

This is the first of two Snort Reports in which I address output options. Without output options, consultants and VARs can't produce Snort data in a meaningful manner. Because output options vary widely, it's important to understand the capabilities and limitations of different features. In this edition of Snort Report, I describe output options available from the command line and their equivalent options (if available) in the snort.conf file. I don't discuss the Unix socket option (-A unsock or alert_unixsock). I will conclude with a description of logging directly to a MySQL database, which I don't recommend but explain for completeness.


Running Snort in IDS mode requires changes to the snort.conf file (here called snort.conf. in order to enable various options. The following diff (a Unix program that shows changes between two files) shows the changes between the snort.conf file shipping with Snort and my configuration file called snort.conf.

cel433:/usr/local/snort- diff -u snort.conf 
--- snort.conf  Tue Apr 24 15:24:48 2007
+++ snort.conf.  Tue Apr 24 15:41:11 2007
@@ -111,7 +111,7 @@
 # Path to your rules files (this can be a relative path)
 # Note for Windows users:  You are advised to 
make this an absolute path,
 # such as:  c:\snort\rules
-var RULE_PATH ../rules
+var RULE_PATH /nsm/rules/cel433
 # Configure the snort decoder
 # ============================
@@ -167,6 +167,7 @@
 # resources:
 # config detection: search-method lowmem
+config detection: search-method ac-bnfa
 # Configure Inline Resets
 # ========================
@@ -194,7 +195,8 @@
 # Load all dynamic preprocessors from the install path
 # (same as command line option --dynamic-preprocessor-lib-dir)
-dynamicpreprocessor directory /usr/local/lib/
+#dynamicpreprocessor directory /usr/local/lib/
+dynamicpreprocessor directory /usr/local/snort-
 # Load a specific dynamic preprocessor library from the install path
 # (same as command line option --dynamic-preprocessor-lib)
@@ -204,7 +206,8 @@
 # Load a dynamic engine from the install path
 # (same as command line option --dynamic-engine-lib)
-dynamicengine /usr/local/lib/snort_dynamicengine/libsf_engine.so
+#dynamicengine /usr/local/lib/snort_dynamicengine/libsf_engine.so
+dynamicengine /usr/local/snort-
 # Load all dynamic rules libraries from the install path
 # (same as command line option --dynamic-detection-lib-dir)

Read part 2, Command line output modes

This was first published in June 2007

There are Comments. Add yours.

TIP: Want to include a code block in your comment? Use <pre> or <code> tags around the desired text. Ex: <code>insert code</code>

REGISTER or login:

Forgot Password?
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy
Sort by: OldestNewest

Forgot Password?

No problem! Submit your e-mail address below. We'll send you an email containing your password.

Your password has been sent to:

Disclaimer: Our Tips Exchange is a forum for you to share technical advice and expertise with your peers and to learn from other enterprise IT professionals. TechTarget provides the infrastructure to facilitate this sharing of information. However, we cannot guarantee the accuracy or validity of the material submitted. You agree that your use of the Ask The Expert services and your reliance on any questions, answers, information or other materials received through this Web site is at your own risk.