Until just a few minutes ago, Softonic, a software download site, was delivering adware that would be installed regardless of whether the user had declined to install it. This threat was embedded in fake UnRarX and VLC installer packages.
These packages purported to install a toolbar that is related to ChatZum. Even if the user declined the offer to install the toolbar, the package would silently install an Internet plug-in called Zako, and would change the browser’s search option to point to ChatZum’s site.
Read more: http://www.intego.com/mac-security-blog/softonic-download-site-briefly-delivers-trojan-adware-installer/