You've probably heard of malware-laden ads causing havoc on the web, but rarely on this scale. Malwarebytes has discovered a malware campaign that was using Yahoo's ad network to target legions upon legions of visitors -- Yahoo's main site racks up 6.9 billion visits per month. While it's not clear what would happen if you fell victim to an attack, the Flash-based exploit kit linked to the campaign typically includes both ad fraud and ransomware. In short, there's a real chance that you could have been locked out of your PC simply by checking on your fantasy sports league.