Apple's updated an entry in the anti-malware files of OS X to lock down a trojan that pretends to be a Flash player installer, but actually hijacks users' search results. The trojan is known as "OSX.QHost.WB.A," and claims to install Flash, but instead redirects Google results to an IP in the Netherlands, which then loads unwanted ads and offsite content along with the fake search results. When the malware was officially discovered, none of the ad servers actually worked, so the malware threat at this time is more of an inconvenience than anything.
Still, Apple apparently doesn't want to take chances -- it's updated the "XProtect.plist" file in OS X with the definition of the trojan. Since an update earlier this year, you don't even need to run Software Update to get this upgrade, as you likely get File Quarantine definitions upgraded daily already. But it's good to know that steps have been taken already to protect your Mac from this malware.