If your Intranet has a connection to The Internet, it is advisable to install the appropriate firewall software to protect access from unauthorised persons who are located outside of your Company.
Most web servers generate logs which are used to determine site statistics.
This is the information that tells you who has visited your site, which pages they visited, how long they stayed at each page, which is the most popular page etc. As I said earlier, it is the exact technology pon which The Internet is built, only this is restricted to users who are within your Company. Hope this helps, best of luck.