Thousands computers around the world have been infected with malware dubbed "Trojan.Milicenso." The malware makes printers spit out pages and pages of garbled content and the malware is dubbed a delivery vehicle for hire. Most of the affected companies are in the US, India, northern Europe, and South America.
The malware is believed to have infected computers in the traditional way such as via e-mail attachments and compromised websites. Once the malware is open it redirects users to pages in several advertisements. Making printers print gibberish appears to be a side effect. The malware unpacks a file on the PC printer queue and Windows turns that into a print job running the printer until it's out of paper or disconnected.