Trend Micro (http://www.trendmicro.com/us/marketing/newsletter/flod/20120420/article1.html)

Recent news of a large-scale Mac malware shattered the illusion that Macs are safe from malware infection once again. This particular malware exploits a vulnerability in Java that allows the execution of malicious routines on vulnerable systems.

What is the Flashback Trojan?

The Flashback Trojan/backdoor is a specially crafted file that exploits a particular vulnerability in Java that allows code execution. Code execution can prove risky as this means any malicious routine can be executed on a vulnerable system. The Flashback Trojan can, for instance, download other malware onto already-infected Macs or run malicious tasks. It can even take over systems without a users’ knowledge.

Infected Macs were mainly found in the United States and Canada