Malware having been a rarity on OS X, it s taking some time to adjust. Microsoft researchers have analyzed a new piece of malware targeting Macs running Snow Leopard. The malware exploits a three-year-old flaw in Office for OS X that Microsoft patched in June 2009. The vulnerability is a stack-based buffer overflow and the malware that Microsoft researchers found is using that bug has an entry point for executing two-stage shellcode that eventually leads to the installation of a bot that connects to a remote command-and-control server.
Source: https://threatpost.com/new-malware-found-exploiting-mac-os-x-snow-leopard-050212/76512/