It's called a router. Get one. My DSL modem goes through a Netgear RT314 router which both neatly splits the line into four and disguises the actual Ethernet address of my computer. The only bad side effect is that I can't run Yahoo Messenger for more than a few minutes before YM disconnects. I don't know how much BlackIce costs, but most 4-port routers these days should cost about $150 and their installation is painless.