Snort FAQ



Snort Installation for the Win32 environment March 2003 by Rich Adamson ( radamson at routers dot com ) and updated in December 2004, March 2006.

Introduction The snort intrusion detection system was written as an application intended for use on a Unix operating system, relying mostly on a low-level independent communications driver referred to as libpcap. Thanks to the efforts by a number of supporters(1), snort has been ported to the 32-bit Microsoft Windows operating systems of recent vintage including Windows NT, 2000, XP and others. Snort requires the same low-level drivers, WinPcap, in order to function on the Windows operating system. (Note: running snort on the older Windows 9x systems should be avoided.)

This README file is intended to document the minimum drivers required by snort. The user may wish to install other snort-related components such as IIS, Apache, or Snortsnarf as well. Installation documentation for those components is available from(2):

Snort Following the installation instructions provided with snort.

WinPcap Driver Snort requires the WinPcap driver to be installed in order to function. Snort has been extensively tested with WinPcap v4.1. The current installation package can be downloaded from: The WinPcap installation will install packet.dll and wpcap.dll drivers in the system32 directory. (Note: if older versions of these two drivers exist, the instructions at the above URL suggests manually deleting them from your system, reboot, then install newer drivers. Do NOT use any of the WinPcap “beta” versions as they are likely to fail.)

LibnetNT Driver Certain snort functions, notably the FlexResp functions, will also require an appropriate version of LibnetNT to be installed in order for snort to operate properly. Snort 2.6 has been tested with the version of LibnetNT version 1.02f. The current installation package can be downloaded from: The snort installation includes LibnetNT.dll driver in the snort/bin directory, and relies on the use the WinPcap drivers noted above to function. (Note: the FlexResp routines were being rewritten as of Dec 2004, therefore please verify that work has been completed prior to attempting to use them.)

Installation Test Steps: The following steps can be used to test the installation of snort and its associated drivers.

  1. From a command line prompt, change directories to where snort was installed (cd \snort\bin)

  2. Execute the following as a way to verify that snort can access the WinPcap drivers: snort -W The result should provide a list of available NIC adapters on the system. If more than one adapter is listed, note the interface number (e.g, 1, 2, 3) of the NIC adapter that you expect snort to use for monitoring/sniffing. If the command does not provide any list, the WinPcap drivers are not installed properly; review the installation procedures provided with WinPcap and reinstall if necessary. (Note specifically the instructions at that suggest removing old versions of WinPcap and rebooting prior to installing a newer version.)

  3. Execute the following to ensure an understanding as to which version of snort is installed: snort -V and note the result (version 2.2, etc.). The specific version number will be required if you ask for assistance from the snort mailing list along with the specific Windows operating system that you are using.

  4. Next, using the interface number noted in step #2, above, execute: snort -v -n 3 -i 2 where 2 should be replaced with the interface number noted. This will cause snort to operate in a basic sniffer mode (-v), displaying the headers of the first 3 packets observed (-n 3) from the interface specified (-i 2). If packets are displayed, snort is functional and can find the low-level WinPcap drivers. If no packets are displayed, either the packet drivers are not installed correctly, or, the interface number (-i 2 in the example above) is incorrect.

  5. If snort is functional, locate and read the contents of the snort.conf configuration file. The default installation places the file in the snort\etc directory. Modify the contents to include: var HOME_NET (replace with your internal network addresses) var EXTERNAL_NET !$HOME_NET (this tells snort the External Network is everything not Internal) var RULE_PATH c:\snort\rules (this tells snort where to find the installed Rules) Save the text file, and execute the following (adjust each directory path to match your installation): C:\Snort\snort.exe -c “C:\snort\etc\snort.conf” -l “C:\snort\Log” -A full -i 2 -d -e -X Note: Be sure to create the c:\snort\log directory on your machine before executing the above. If the above command line entry does not return to a command line prompt, then snort is running, listening to all packets on interface 2 (-i 2), dumping those packets that match the Rules to files in the C:\snort\Log directory. If after executing the above, snort aborts and returns to a command line prompt, carefully read the data that snort sent to the screen as it will suggest configuration and rule errors, etc.

  6. Carefully READ the documentation included in the snort installation, including: snort\doc\snort_manual.pdf snort\doc\FAQ Note: these two references (along with other text files included in the snort\doc directory) should answer 95% of your initial questions.

Technical Notes: 1. Snort was written using the C programming language calling various routines provided in the libpcap.lib and packet.lib libraries. If an old version of WinPcap exits on your Windows system, newer versions should be installed from the URLs noted above. At the time this document was written, snort v2.2 functioned properly on Windows 2000, 2003, and Windows XP systems with: system32\packet.dll version reported: dated April 4, 2003 size: 57,344 bytes system32\wpcap.dll version reported: dated April 4, 2003 size: 1208,896 bytes snort\bin\LibnetNT.dll (no version reported) dated May 2, 2003 size 68,161 bytes

  1. If you intend to run snort on a multiprocessor Intel system, WinPcap v3.0 or higher is required. Earlier versions of these libraries did not support the multiprocessor systems. Do NOT attempt to use any of the WinPcap “beta” versions as snort will likely fail.

  2. If you intend to run snort as a Win32 Service, ALWAYS run snort from the command line FIRST to ensure there are no configuration or rule errors. Snort will NOT report errors when run as a Service; it will simply abort providing no clue why it aborted. The syntax for running snort as a Service can be seen by simply executing snort from the command line (no command line parameters) and reviewing the first several lines displayed.

============================================================= (1) Contributors to this README file include: Rich Adamson Chris Reid

(2) Installation Documentation for other Snort-related components: Michael E. Steele, ( ) has prepared, written and maintained several excellent documents integrating other snort-related components. The documents can be downloaded from: As of March 2003, the following configuration / installation documents were available: Snort with IIS and Snortsnarf Snort with MySQL, IIS and ACID Snort with Apache and Snortsnarf Snort with MySQL, Apache and ACID Snort with Slave and Snortsnarf Snort with MySQL, Slave and ACID