IBM X-Force is reporting a spike in image-based spam, reaching 15-22% of all spam. In 2007, image-spam content was pushing penny stocks as part of pump-and-dump schemes. Today, the cybercriminals behind image spam runs are selling drugs. Most of them ask the user to visit a.com Web site with a domain name consisting of six digits like 123456.com, and the user has to manually type that URL into the browser.
Source: https://threatpost.com/return-image-based-spam-050509/72623/