Background briefing – web servers and logs

At its heart, the World Wide Web is a vast collection of computers that handle the HTTP protocol. The HTTP protocol defines a request message and a response. A web server handles these requests, creating appropriate responses. This activity is written to a log, and we're interested in that log.

When we interact with a complex web site for a company that conducts e-business—buying or selling on the web—it can seem a lot more sophisticated than this simplistic request and reply protocol. This apparent complexity arises from an HTML web page, which includes JavaScript programming. This extra layer of code can make requests and process replies in ways that aren't obvious to the user of the site.

All web site processing begins with some initial request for an HTML web page. Other requests from JavaScript programs will be data requests that don't lead to a complete HTML page being sent from the server. It's common for JavaScript programs to request JSON...