Popcash is a prolific ad network (over 180M hits/month according to SimilarWeb) being used by online fraudsters to distribute malware and other nuisances. Malwarebytes Anti-Exploit users were protected from this attack: The Magnitude EK is pushing crypto ransomware, possibly one of the worst strains of malware because it uses genuine encryption to lock down a users personal files. We contacted Popcash on two separate occasions through their official report malware campaign, but never received a response.”]
Source: https://blog.malwarebytes.com/threat-analysis/2015/06/popcash-malvertising-leads-to-cryptowall-3-0/