Apple is much less forthcoming about the specifics of its internal security efforts.

Microsoft has disclosed information about its Security Development Lifecycle, both to encourage confidence and to promote the development of more secure software across the industry. Both devote considerable time and resources to removing security-related faults in their own software and preventing the introduction of new ones. Over the years both Microsoft and Apple have taken many measures to reduce the risks from malware. Mac users tend to be wealthier than average and are likely to be more heavily concentrated in wealthier developed countries, which may attract malware authors to Macs. While that is still the case today, the relative payoffs have changed substantially. So back in 2009, Windows represented a far larger target than Mac for profit-seeking virus and malware authors. Most of the rest now comes from smartphones and tablets running Apple’s iOS and Google’s Android.

By July 2015 Windows had dropped to 41.7% and Mac to 5.4%. In April 2009 (the earliest date from which records are readily available) nearly 90% of traffic came from computers running Windows, compared to only 6% for Mac. Definitive statistics for the market share of operating systems are hard to come by, but one useful estimate is available from the server traffic records of Wikimedia (the non-profit organisation that runs Wikipedia).

Windows vs mac market share