Vundo.gen.o is annoying infection that can be avoided easily by not checking out spam emails. Vundo.gen.o is a trojan+adware combination.

Vundo.gen trojan is distributed via spam messages. Once user clicks on a link provided on spam email, he visits an infected website. The website then installs Vundo.gen.o with no asking for permission. The trojan downloads additional malwares and shows enormous amounts of pop-ups.

Source: http://www.spywarevoid.com/vundogeno.html