Malware is more commonly found on iPhones that have been jail broken. Windows Mobile takes the cake when it comes to attracting malware via SMS. BlackBerry suffers from the multitasking concerns that make it easier for malware to run unnoticed. Android is the only open source operating system discussed here. The developers of BlackBerry have done an excellent job of keeping the sensitive inner workings of this smart phone a secret from the public. There is not a lot of information regarding malware for this operating system, although it is the oldest of the most popular outside of America.”]
Source: https://www.csoonline.com/article/2129760/which-smartphone-is-the-most-secure.html