It's not this site. You'd probably had that virus/trojan a long time ago. It just made it's attack on that particular time.
Google analytics is a great way to learn more about your site and improve it btw.
Google analytics: http://www.google.com/analytics/Basically it tracks where users come from (what search engine, cost-per-click advertising, website link etc.) and what pages they visit. I don't believe it installs any software/spyware on the users computer.Tons of sites on the web use it to evaluate their online marketing efforts.Steve