Apache web servers have the innate ability to issue user tracking cookies through a module called mod_usertrack. In order to utilize these tracking cookies, your Apache installation must have mod_usertrack enabled. Standard Apache installations sometimes come with mod_usertrack either compiled into the Apache httpd binary or built into Apache as a Dynamic Shared Object, also referred to as a DSO. Mod_usertrack must exist in either form for Apache to issue cookies.
NetIQ, the people who now own the Webtrends software, have a knowledge base article on:
How do I configure Apache web servers for user-tracking Cookies. It is quite in depth and I'll report back if/when I get it working.