We spent some time trying to remove a nasty bit of malware code from one of my client’s servers today. On their windows server, this virus used javascript to create a list of invisible links (in an i-frame) to bugged websites in the page footer. On their Unix/Linux accounts, the virus added redirects to .htaccess files which will send you to similar sites. It also adds a nasty bit of javascript just after the header tag.
Webmasters, you may want to check the code on your index pages to see if anything unusual is lurking there. From my research, it sounds like this was a client side security issue with the Chrome browser.