Malicious advertisements on domains belonging to Disney, Facebook and others are leading people to malware that encrypts a computer’s files until a ransom is paid, Cisco Systems says. Cisco’s investigation unraveled a technically complex and highly effective way for infecting large number of computers with ransomware, which it described in detail on its blog. The finding comes shortly after technology companies and U.S. law enforcement banded together in a large operation to shut down a botnet that distributed online banking malware and “ransomware””]