For defence, you roll Response and Stealth.
Rollplay-Argumentation: Stealth is a program to hide someones icon from other matrix units. Hence, it is harder to see and therefore hit him. For example by changing the port adress, making copies from oneself as decoys, appear as data files, etc. Response indicates how fast someone can find new hiddeouts/change the appearance. The other icon constantly looks for and finds the hacker, therefore the hacker then has to find a new hiddeout or change his appearance.