Daily Archives: 30 August 2005

Mozilla Prefetch Misgivings

I’ve recently noticed that when I go to Google to search on something, I will sometimes get a cookie request from the first link that Google finds in the search.

I thought this was strange since I didn’t click on the link to the first search response. In fact, I hadn’t clicked on any link. Yet, I was being asked to accept a cookie from the site as if I had.

Well, now we know what is going on. The Mozilla family of browsers (which includes Firefox) implement an HTML tag that prefetchs content. The Mozilla FAQ says:

Link prefetching is a browser mechanism, which utilizes browser idle time to download or prefetch documents that the user might visit in the near future. A web page provides a set of prefetching hints to the browser, and after the browser is finished loading the page, it begins silently prefetching specified documents and stores them in its cache. When the user visits one of the prefetched documents, it can be served up quickly out of the browser’s cache.

So, this is how, when using Google, Mozilla prefetches documents and stores it on your computer, without your knowledge or approval, even though you haven’t clicked on any links found by your search.

In this day of super spammers, porno purveyors, and virus vermin, it doesn’t take a genius to figure out that this is a vector for BigProblems(tm). Imagine the police taking you and your PC to jail because of illegal content downloaded and stored on your PC without your knowledge or consent. Imagine Trojan Horses or viruses being downloaded without your knowledge or consent.

While you can turn this “feature” off (and I urge you to do so by following the directions from Google here), I think it should be off by default. This is so obviously a problem, rather than a feature, that you have to hope that Mozilla hasn’t begun to emulate Microsoft’s evil ways.