SiteAdvisor is a browser extension for Firefox and Internet Explorer which enables you to check how safe a web site is. It cross-references the domain of the web site you are viewing with a database on the SiteAdvisor web site and then notifies you of its score.
With the extension installed, a button appears in your toolbar (IE) or status bar (Firefox) which changes colour depending on how safe the site is. Sites that have passed its automated tests are green, sites which you may potentially have issues with are yellow and sites which have confirmed issues are red. These may be sites with lots of popups or that try to install spyware. Sites may also appear grey if they have yet to be checked. Clicking on the button lets you view a more detailed report that says which factors lead SiteAdvisor to give the site its rating.
It also overlays Google search results, by putting marks beside each site. As you can see in the screenshot, I did a search for a popular spyware-free file sharing client and several of the sites had red marks, mostly for being fake sites wanting money for software that is actually free. Many of those were sponsored listings, which is a bit scary.
It looks like quite a useful extension and probably one I would keep. I don’t tend to browse dodgy sites but it’s better to be safe than sorry. I would, however, have liked the ability to move the button to my toolbar instead of the status bar, as I already have Adblock, Greasemonkey and mozCC there so it gets a bit full from time to time.
Update: The extension has now been updated and is now fully branded as being part of McAfee. It also means that the SiteAdvisor button in the status bar is even bigger now, and you still can’t move it. 🙁