CR: 3.4.7.a - ICE subs fire #2015
Description
Ice are the only cards with subroutines. A piece of ice may have any number of subroutines in its text box, each one indicated by the [sub] symbol.
a. A subroutine on a piece of ice is a required conditional ability that resolves while that ice is being encountered, usually during a run. See rule 6.5.5.