Envoy - A Linux Application Level Firewall

Envoy - An Application Level Firewall For Linux

Envoy allows for the simple creation of powerful firewalling rulesets using an intuitive gui interface for the creation of rules on an application basis.

Features:
Blocking/Allowing TCP connections on an application basis
Hash calculation to confirm file integrity
GUI (Envoy can also operate without one)
Multi user support
Kernel module based technology
Widespread compatibility due to the use of C and Wxwidgets
Tested with KDE and Gnome on different 2.6 series kernels

Why do I need this?
Control applications. Make sure they only go where intended. Mail client to mail server. Browser to proxy. Nothing else
F.ex. exploited mail client can't connect to attacker because it may only connect to mail server
Interesting to see Acrobat phone home. Or Firefox. Or ...