You need to uninstall Snort.
If you installed Snort using an RPM file, uninstalling is simple. First, determine the RPM installation name by typing the following:
[root@frodo root]# rpm -q snort snort-2.2.0-1
Then use the RPM erase option:
[root@frodo root]# rpm -e snort-2.2.0-1
With the source version, it is just as simple (provided you kept your source tree) in the directory that contains the Makefile, as root type:
[root@frodo snort-2.2.0]# make uninstall
And it automatically uninstalls.
In earlier versions of Snort, there is no make uninstall command available, you should have a look through the Makefile, which will tell you what files have been installed where; it is then a matter of deleting them by hand.
Alternatively, if you had the foresight to install all of Snort into a specified directory, rm -rf is also a very effective method of removing all traces.
Don't forget that if you have modified your startup scripts to start a Snort daemon, these need to be changed to reflect the removal of Snort.
If you have not kept your source around, you can install the source, recompile it, and run make install, followed by make uninstall to uninstall.
RPM utility manpage
Upgrading Snort on Linux
Installing Snort from Source on Unix
Logging to a File Quickly
How to Build Rules
Detecting Stateless Attacks and Stream Reassembly
Managing Snort Sensors
Generating Statistical Output from Snort Logs
Monitoring Network Performance