A security researcher said that a malvertising campaign could affect as many as 50M users, it affected some popular web sites like Facebooks Bejewelled Blitz. A large-scale attack is meant to hit the OpenX platform (Online Advertising Technology) Malvertising campaigns exploiting brand new vulnerabilities are optimal for cyber criminals because they require almost no effort, and this obviously means lower costs. Security professionals have to create layers and layers of defense, the higher the cost is for the cyber-criminals, the more difficult will be for them to operate.”]
Source: http://securityaffairs.co/wordpress/37816/cyber-crime/50-million-users-malvertising.html