The first time I heard about Alexa was through our anti-spyware program. It identifies a standard registry key included with Internet Explorer as “Data Miner” spyware, with little explanation, and offers to delete it. With the exponential trend and growth of the blogosphere today, Alexa surfaced again, here, as it is the most used base measure of web site traffic and rankings, the best known for operating a website that provides information on the web traffic to other websites. But is alexa a spyware?

According to Alexa it is not a spyware that generally collects your personal information for advertising purposes, and provides you with no value in return. Alexa collects information from users who have installed an “Alexa Toolbar,” allowing them to provide statistics on web site traffic, as well as lists of related links. The Alexa Toolbar is only installed when a user chooses to download it – it is not installed without your knowledge. The Toolbar is not hidden; it is prominently displayed at the top of the browser. In order to fill the Toolbar with relevant information, the URL of the page you’re on is transmitted to them and they return related information for that page. When the Alexa Toolbar is turned on, Alexa collects and stores the URLs you visit as your Toolbar requests data to display about these URLs from our servers. These URLs may include information about the Web pages that you view, the products you purchase online, and the data you enter in online forms and search fields. The Alexa Toolbar can be turned off at any time. Turning the Toolbar off prevents any information from being transmitted to them.

So how did my spyware found Alexa? Part of the reason is that there is a registry entry from Alexa built into every version of Internet Explorer by Microsoft (up to the XP Service Pack 2 release)–this registry key is associated with the Related Info Sidebar, accessed from the Tools menu in IE, the ‘Tools’/'Show Related Links’ menu item (and a corresponding toolbar button if you added it from the ‘Customize…’ link on the toolbar). When you request Related Information for a site, the URL of the site you are on is sent to Alexa’s servers, which in turn provide data about the site you are on at the time. If you use that feature, IE will contact the Alexa servers, via MSN, to obtain information about other web pages that seem to be related, open an Explorer Bar, and display those (plus adverts and whatnot). And due to a bug in IE (versions prior to IE6 on XP SP2), you might even transmit (potentially sensitive) URL information if you reload pages long after you close the Explorer Bar, about (even secure HTTPS/SSL) pages for which you didn’t request Related Links. But if you don’t use that menu or button, Alexa will not hear from you and no spying will take place. The extent of what Alexa “spies” is that someone in the world using Internet Explorer requested information on the specific URL.