Though UNIX-like systems such as Mac OS X and Linux can claim fewer threats due to their smaller user bases, threats do still exist. Viruses can be the least of your problem too. Ransomware, like the recent version of KillDisk, attacks your data and asks you to pay, well, a king’s ransom to save your files. (In the case of KillDisk, even paying the ransom can’t save you if you’re running Linux.)