IPCop Firewall is a Linux firewall distribution geared towards home and SOHO (Small Office/Home Office) users. The IPCop interface is very user-friendly and task-based. IPCop offers the critical functionality of an expensive network appliance using stock, or even obsolete, hardware and OpenSource Software.
IPCop Firewall basically sits "in between" your Internet connection (dial-up modem, cable-modem, DSL, etc) and works directs traffic using a set of rules for the TCP/IP traffic that underlies all Internet activities.