During a recent presentation I was asked a rather astute and interesting question. The audience member compared the information security world to the biological world, and wanted to know why, when parasites fill every biological niche in the ecosphere, the niche of Macs has not been infested with malware. I have now forgotten what I said in response, but I do remember thinking at the time my answer was bullshit.
The correct answer is as follows: The biological analogy frays at the edges when you consider monetized malware. Parasites inhabit every biological niche because their only goal is to propagate the species, not be the biggest species out there. Malware writers' goal is to make the most money, and will spend their energy creating attacks that allow them to make the most money. The motive of profit maximization causes them to abandon portions of the target space entirely. In terms of the biological argument, consider a parasite was not rewarded for continuing its species, but instead was rewarded for the number of infected hosts. If the parasite had the opportunity to make the split decision between producing offspring that can infect coelacanths or infect beetles, which would be the better strategy?