This article. while probably not much of a surprise – we have seen this type of thing before, does highlight a couple of valuable points to consider.
Your phone is essentially a listening device that permits you to make phone calls. There is a denial by the agency that this took place, but given the research behind this and the fact that if you search for spying/eavesdropping apps in the Google Play store you will find a selection of spying apps that you can purchase today, I think that is reasonable to assume this is more than plausible. If you are a nation state or just needing to conduct sensitive business discussions, phones can pose a risk.
Your users are your weakest link. No matter what sophisticated countermeasures you put in place they will always be undone by a user wanting to see the animated dancing bunny or some other cool thing on the Internet. Security awareness training can help, but it is sometimes not sufficient these days. Analyzing the environment the users are in and adjusting security controls appropriately is sometimes needed.
Don’t trust the app store. Google has had major issues over the years but Apple is not immune either. Both are getting better, but so too are the attackers.
https://www.nytimes.com/2018/01/18/technology/lebanese-intelligence-spy-android-phones.html