Snort IDS upgrade and tips on the Snort.conf file

Expert advice for security resellers and consultants on the productive use of Snort IDS, with details on the Snort upgrade and snort.conf file functions enabled by default -- such as IP ranges, ports of interest and preprocessors.

Since the last edition of Snort Report, Snort IDS has been updated from version 2.6.1 to So I'll begin this edition by addressing the issue of upgrading from one version to the next. Then I'll move on to discuss the contents of the snort.conf configuration file.

In my last Snort Report, I recommended creating a directory specifically for Snort 2.6.1, namely /usr/local/snort-2.6.1. That directory contained the Snort binary, in the bin/ directory. To "upgrade," create a new directory for Snort, e.g.:

freebsd61-generic:/root# mkdir /usr/local/snort-

Now proceed with the steps to retrieve, extract and compile Snort described in the previous article. Be sure to replace instances of "snort-2.6.1" with "snort-". To run the new version instead of the old, invoke it from the /usr/local/snort- directory.

I recommend creating new directories for extraction and installation every time you encounter a new version of Snort. At the very least, you will have a chance to keep the old version running while creating a new version for testing. Of course, you should deploy a separate testing infrastructure independent of production systems. Keeping several versions of Snort handy on production systems, however, is a good way to roll back to an older version should a newer version seem to encounter difficulties in the field.

Snort: Understanding the configuration file

 Introduction: Upgrade to Snort
  The snort.conf file
  Defining IP ranges of interest
  Defining ports of interest
  Core preprocessors
  Non-dynamic preprocessors

About the author
Richard Bejtlich is founder of TaoSecurity, author of several books on network security monitoring, including Extrusion Detection: Security Monitoring for Internal Intrusions, and operator of the TaoSecurity blog.

This was first published in April 2007
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