This FBI alert identifies CryptoWall as the most current and significant ransomware threat targeting U.S. individuals and businesses. CryptoWall and its variants have been used actively to target U.S. victims since April 2014.
These financial fraud schemes target both individuals and businesses, are usually very successful, and have a significant impact on victims. The problem begins when the victim clicks on an infected advertisement, email, or attachment, or visits an infected website. Once the victim's device is infected with the ransomware variant, the victim's files become encrypted.
In most cases, once the victim pays a ransom fee, he or she regains access to the files that were encrypted. Most criminals involved in ransomware schemes demand payment in Bitcoin. Criminals prefer Bitcoin because it is easy to use, fast, publicly available, decentralized, and provides a sense of heightened security/anonymity.