An inbound-only firewall is not 100% effective at catching a hacker’s every attempt to access your computer.
An inbound firewall prevents Internet attacks such as hackers from coming into your computer. Any suspicious or unauthorized communications are filtered by the firewall. However, if these threats get through your firewall your personal data could then be transmitted back out to the hacker. To catch these thieves on their way out your firewall must be capable of automatically blocking unauthorized outbound communications - “outbound protection”.
Some firewalls don’t have what’s called “outbound protection”. That means they can’t control information that leaves your computer. This is risky, since hackers have ways around inbound firewalls. The ZoneAlarm outbound protection references our constantly updated database of trusted programs and program behavior—so the ZoneAlarm firewall can make security decisions safely and automatically.
At ZoneAlarm, we added outbound protection and then went beyond that to create the equivalent of guards who are trained to spot and stop suspicious behavior. We call this the OSFirewall, because it goes where dangerous programs go—to the operating system level. It monitors program installation, registry and file changes, keyboard and mouse code control, and over 40 other potentially dangerous behaviors.
Note: Outbound protection (Program Control) and OSFirewall are not included in the basic ZoneAlarm free firewall.