For most of the recorded history of malware, viruses, Trojans and other malicious software have been specialists. Each piece of malware typically targeted one platform, be it Windows, OS X or now, one of the mobile platforms. But the last few months have seen the rise of cross-platform malware that have the ability to infect several different kinds of machines with small variations to their code. One recent example is the Crisis Trojan, which can infect both Windows and Mac OS X machines. One thing that s helping drive this trend is the existence of vulnerabilities in apps such as Java that are installed on several platforms.
Source: https://threatpost.com/rise-cross-platform-malware-082412/76947/