Using a firewall in android
A lot of apps do not really need web access and work fine without such access. With many android apps, especially games, browsers, and the like having spyware elements that phone home, how effective is using a firewall to protect one's data? I ask because I am not familiar with the inner workings of android and wonder if apps can bypass firewalls in android. I use Avast Mobile Security which includes a firewall but wonder if - in android - data goes out anyway. Does it? How secure or insecure should I feel? Thanks.