Ice can be installed in front of any server in order to protect that server. After a piece of ice is installed in front of a server, it is dedicated to that server and cannot be moved or rearranged.
When the Corporation installs a piece of ice, he must install it in the outermost position of the server and pay an install cost equal to the number of pieces of ice already protecting that server. The outermost position is the position farthest from the server, in front of any other pieces of ice that are protecting the server.
Ice is defensive software the Corporation installs in front of his servers to protect his valuable data. There are four main subtypes that can appear on a piece of ice: sentry, barrier, code gate, and trap. Ice also has separate abilities called subroutines.