A firewall is a software program or piece of hardware that helps screen out hackers, viruses, and worms that try to reach your computer over the Internet. Usage of this tag may be aligned to users concerned with suspected malware creeping into their devices, setting a filter to allow certain applications to access internet and general monitoring of incoming/outgoing network connections
What is a Firewall and How Does It work?
A firewall is a system that provides network security by filtering incoming and outgoing network traffic based on a set of user-defined rules.
In general, the purpose of a firewall is to reduce or eliminate the occurrence of unwanted network communications while allowing all legitimate communication to flow freely.
Now Internet access of all apps can be adjusted. The apps won’t be able to go online without you knowing and send any data.
In addition, by using firewall, you can allow some apps to go to the network only via mobile Internet (some firewall apps even distinguish roaming), while others (for example, ones that require a lot of traffic) – only through WiFi.
Wile root-apps can do that directly at system level (usually via iptables), non-root solutions facilitate Android's VPN feature – which usually means you cannot use other VPN apps simultaneously as Android only allows a single VPN to be active.
