Tell Facebook users at your house to be very alert when social-network friends seem to say they've just got to check out this or that video. That scenario happens all the time - which is why it's used by social-engineering hackers to infect social networkers' computers. Where the new worm comes in is an extra step for which users need to be on the alert. The way it works is, they get a link supposedly to a video, CNET reports. That takes them to a Google page where they read that, in order to view the video, they need to click to download some code or an app. Clicking on that link installs Trojan software. The link on that page, however, isn't really a Google link. CNET explains why and how Google pages are being used. Though the problem will probably be fixed by both Google and Facebook shortly, this is a good illustration of why social networkers should never blindly click around - especially when there's a cool video in the offing.