Ad-injecting trojan targets Mac users on Safari, Firefox, and Chromearstechnica.com/apple/2013/03/ad-injecting-trojan-targets-mac-users-on-safari-firefox-and-chrome/
" It's not a particularly sophisticated malware, but the fact that there is a piece of code sitting in the browser and monitoring every single piece of information is scary and dangerous, Botezatu said. Criminals can change their approach at any time, and while they may be injecting ads today, tomorrow, they could switch to injecting exploit code or directing users to phishing sites and drive-by-download attack sites. The malware's structure can also be modified to display malvertisements or steal browser cookies, Botezatu said.
"It's also not limited to just Mac OS X, as Symantec has previously identified a Windows version of Yontoo. Adware for Mac OS X has been increasing for some time, and Mac users need to be vigilant about what applications they download and install so that they don't inadvertently infect themselves. ..."