MacRumors posted a story that Apple has updated its "Xprotect" anti-malware system to recognize Yontoo and warn users who attempt to install it on their machines

Apple routinely uses its Xprotect anti-malware tools introduced in OS X Snow Leopard to provide rudimentary protection against threats, and has expanded its efforts in OS X Mountain Lion with the introduction of Gatekeeper to allow users to restrict app installation to software from identified developers registered with Apple, or even to only apps installed through the Mac App Store. Apple has also been using Xprotect to enforce minimum version requirements for plug-ins such as Java and Flash Player, forcing users to upgrade from earlier versions known to have significant security issues.

 Apple Updates OS X Anti-Malware Definitions to Block 'Yontoo' Adware