UsaProxy is based upon an HTTP proxy approach. Logging is automatically done on an intermediate computer lying between the web browser and the web servers while multiple users surf the web. The assumption is that all page requests, the browsers make, go through the proxy.
In particular, what is intended to happen is the following:
Small sample of the log output produced by UsaProxy:
220.127.116.11 2006-08-27,21:03:00 http://www.kiko.com/ load size=862x389
18.104.22.168 2006-08-27,21:03:03 http://www.kiko.com/ click coord=249,195 dom=abaaaa
22.214.171.124 2006-08-27,21:03:24 http://www.kiko.com/ mouseover coord=341,164 dom=abaaaaa img=kf_index.gif
See a sample log file (7KB).