A recently discovered bit of malware for the Apple Mac OSX operating system presents an opportunity to make a few brief points. I'll try not to preach. Too much.
The short version; The Peer-2-Peer file sharing networks have been discovered to be spreading a trojan horse software (link) posing as a free or cracked version of Apple's iWork 2009 (link) suite of productivity software. Apple does have a free trial version available for download for those who would legitimately like to try it out on their Mac.
For Heaven's Sake; Practice Safe Hex
Do not download from anonymous P2P networks. Forget the moral and ethical arguments entirely. These networks are simply a playground for people who would like to spread malware. All one has to do is create a trojan horse, and give it a name that suggests it is a crack for some expensive software, and off it goes. The prevalence of broadband connections means people will even download a 300 Megabyte piece of malware, which might actually be embedded within what appears to be the 'real' item claimed. The nature of most P2P networks makes it somewhat difficult to figure out where something came from, so there's little recourse when you get infected.
Note that I said anonymous networks. In fact, you should always exercise caution with any software, no matter the source. But at least when you know the source, you have someone to go to and say, "Hey, your download of XYZ Express v 11.3 was infected with the ILoveYou virus!". When downloading something from a legitimate source, one should check the verification methods, such as the hash/fingerprint value published for it. And certainly if you have any suspicion about a file's contents, be sure to scan it with updated tools of the appropriate sort - the more the better.
I could make analogies here of having unprotected carnal relations with certain ladies of ill-repute who work the least savory parts of otherwise less-than-healthy burghs. Don't make me go there.
No Such Thing as a 'Secure' Operating System
Computer security is a balancing act; security against usability. The only truly secure system is one that is impossible for anyone at all to access, in any way whatsoever. Knowing that this is useless, most try to aim for something somewhat less secure than that. So, users must be given access. Access to execute programs and read/write data is a given. Access to change system settings and install software is needed for administrators and/or power users. In an ideal world, every authorized computer user could have effectively full access to their systems, to do whatever they want, whenever they want. But this is not an ideal world. This is a world where people connect to P2P networks and download supposedly 'cracked' software, and then proceed to execute it with administrative privileges.
Computers today contain mechanisms to try to protect the computer against the user. Anti-Virus software, User Account Control, separate administrative/user accounts, prompts when a program tries to perform an administrative action; all these are attempts to have the computer warn the user, "What you are about to do might be bad. Really bad." But none of those mechanisms do a thing when a user ignores all common sense, forgoes even the smallest attempt to verification, and goes ahead and allows that software from an anonymous source to run on their computer.
It does not matter what operating system you use. You must use it intelligently. The malware in question here appears to be fairly open-ended, in that all it is meant to do now is 'call home' to check for updates for itself. Unlike previous similar Mac malware, it does not pull simple tricks that give it away like showing advertising popups. Assuming it was created properly, it could be the start of a Mac botnet. That means an infected computer might, potentially, be used for anything at all the malware author decides in the future.
Would anyone here like a slightly-used soapbox?