Half-Life is a series of popular computer games. See http://half-life.com
The default server port is UDP 27015 and the default client port is 27005. The game allows manual entry of the destination port when connecting.
l7-filter uses the quake-halflife pattern for Half-Life 1. This should also match other games that use the same engine, including Counter-Strike v1.6, Counter-Strike: Condition Zero, Day of Defeat, Team Fortress Classic, Deathmatch Classic and Ricochet. This pattern has been tested with QuakeWorld (2.30), Quake 2 (3.20), Quake 3 (1.32), and Half-life (18.104.22.168).
l7-filter uses the halflife2-deathmatch pattern for Half-Life 2 Deathmatch. This pattern is tested and is believed to work well.