Although I find most anti-virus software annoying and resource-hogging (looking at you, AVG and McAfee) , I've used Lookout for quite a while, on different phones. It does things besides monitor for threats. One added feature to the pro version is that it can create a basic VPN. If I am in Starbucks for example, the Starbucks app naturally wants me to log on to free WiFi. My Note 5 detects an insecure, unencrypted network, and Lookout defaults my device to a VPN connection. Makes me feel a lot more more secure.