How can I remove Yahoo trojan?
Several time an hour, the screen below pops-up, asking for my Yahoo email password. Once, when I did submit my password, a spam email was immediately sent to all of my friends. I changed my password but can't get rid of this popup. I don't know if it's a trojan or something else, but if someone could help me get rid of this screen, I'd really appreciate it.
iMac, Mac OS X (10.7.3)