For analyzing Apache HTTP server logs (access_log) various tools were created using the Perl programming language.
For example to obtain the number of hits from a host withing a certain time interval, an overview of URLs linking to objects on the web server (referers [sic]).
The latter can also be used to detect bandwidth theft, ie. remote linking to, for example, images.
I've made three small FLOSS examples of access log analyzing tools written in Perl available on my personal website: