Each defensive program has a "Buffer Size," listed in the program statistics. This represents the amount of damage it can intercept before damage begins to deplete the firewall of the node on which it is installed.
Two ICE Walls cost the same disk space to install as one Protector. It takes an additional 3.5 seconds to install the latter. A level 1 Protector will regenerate the equivalent buffer of a level 1 ICE Wall in less than 9 seconds. A level 21 Protector will regenerate the equivalent buffer of a level 21 ICE Wall in about 4 seconds.
Defensive programs cannot be used in stealth attacks.
Once the buffer of a defensive program is depleted, it is removed from the node, freeing up a slot to place another program. Programs can also be removed manually by selecting the node and tapping the program.