This is somewhat fuzzy to me, but I would tend to answer “no”.
IC is similar to Difficult Terrain in the Warfare rules. IC is a hazard that you encounter while moving between quantronic zones, not something that comes into play when attacking or defending. In Warfare, you need to make an Acrobatics roll to enter a zone that has difficult terrain. In Infowar, you need to make a Hacking test to enter a zone with IC without setting off the IC’s effect.
The IC would trigger if the player was actually moving into hacker’s quantronic zone. Say for example, the hacker had valuable information on his commlog. To get that information, I have to actually penetrate your commlog and root around in it. I have to enter the commlog’s quantronic zone to do so.
If the player was simply being quantronically attacked, then his zone isn’t being penetrated, and the IC wouldn’t trigger. Same thing on a “guard” reaction.
The advantage you get on the guard reaction is that hopefully your hacker has a better hacking skill and a higher firewall than whoever he’s trying to protect.
At least that’s how I’d run it.