While ransomware has sadly been a reality on smartphones and Windows PCs for a while, you haven't really had to worry about it on a Mac... until now, that is. Palo Alto Networks claims to have discovered the first known instance of OS X-oriented ransomware in the wild, "KeRanger." If you install software infected with the code (in this case, a version of the BitTorrent client Transmission), it'll encrypt your files after three days and demand that you pay a digital currency ransom to regain control.
In practice, you're likely already safe from KeRanger. Transmission has released a new version of its app that should be safe, and Apple has revoked a security certificate from another developer that KeRanger used to slip past OS X's native defenses. Even so, this is a not-so-friendly reminder that malware of all stripes can potentially infect any given platform -- you can't assume that your operating system's inherent security features (or simply avoiding the most targeted platform) will keep you safe.