Now Macs are being vulnerable to trojans that used to effect Windows for years.
How this works is when someone opens a Word document attachment on their Mac, the trojan kicks in and steals information. Latest victims of this trojan were two NGOs. The trojan creates a connection to the remote server and transmits user info and password which in turn opens a backdoor to the infected system. More info here.
This just proves what has been around for a long time that more popular a platform is, greater is it’s vulnerability to external attacks. Macs aren’t really as secure as constantly advertised, it is just that they were used less and now due to growing user base are facing and will face similar problems that Windows systems do.