Malvertising and ransomware make a powerful and dangerous combination. This article from Network World discusses the evolution of the CryptoWall ransomware tool.
Malvertising is the technique of using banner advertising networks to deploy drive-by malware downloads to the target. This spreads the attack across many thousands of legitimate websites without their knowledge.
Ransomware is malware that encrypts files on the victim’s computer, then demands payment to receive the key to decrypt them.
Passages and Nfusion provide effective protection against this kind of attack by using a hardened operating system which is much more resistant to attack, and by isolating the browser to ensure that any malware would be unable to access your important files anyway.