So you think your mobile is safe and that you are protected by your antivirus! Well, your mobile is safe until you give the permission to share your data. Upon installing applications like TrueCaller, you give the application access to your address book. Thus the application uploads all your contact cards and stores your address book into the company’s server.
So all your contacts are shared. All your family contacts are shared. All your friends contacts are shared. All you business contacts are shared. What happens to this data?! This is shared with millions of people around the world without the consent of your contacts (family, friends, business contacts, acquaintances).
Most probably this data will become the biggest centralized contact data storage in the world (always updated). Truecaller might sell premium services to customers who are willing to pay for such data.
So in other words, YOU are a big threat to your data by giving such applications access to your info and data.