Had similar "false" popup alerts on cruisecritic dot com - IE scripts from their ads, prompting one to do a "free" scan - depending on what AV security product(s) and OS being used - IE 8.0 and 9.0 running AVG seemed to getting them, Firefox with aVast seemed better. AV's updated signature file sometimes set off the warning too, had forwarded the reports to their support for review.

Best practices are to do periodic deep & full scan of hardware & drives using different products if desired, to spot unusual activities and review router/firewall logs for outbound traffic/open stealth ports, etc. On our home server, we pull the broadband connectivity at times to stop all network traffic - threats can do much harm when it's isolated & contained within, offline to the "outside world".

Amazed that most tablet & ipad users run their tech toys with virtually no "defenses" whatsoever unlike the desktop, laptop & netbook generation ... often on open, unsecured WiFi network.