There isn't any verbiage describing IC targets MARKs (that I can find). Also both MARKs and Personas are entities that can be individually targeted and discriminated. I read: [That IC] [targets] {with it's attack option} [your MARK], which doesn't make sense. Each IC does one "thing" as its "attack". None the IC (that I'm aware of) interact with MARKs, just Personas by inference.
As I see it, that's kind of the point, actually. The IC attacks the MARKs thinking that they are you, and it has no effect, their attack can't do anything (except
maybe erase the MARK), because that's not what the IC does.
Also aren't MARKs on a Host inherited down? If you place a MARKs on a Host wouldn't you have a MARKs on everything "slaved"* to it?
*[insert age old discussion on Hosts here]
Only up, page 233 where it talks about PANs and WANs. Just because you have a MARK on the Host doesn't mean you have a MARK on every single file on the Host. That's why you still need to find, MARK, and crack files when you're looking for Paydata.
And as I mentioned before, you could also rule this effect as being that anything that you have MARKed would be the thing targeted, so you MARK the Security Spider, and suddenly the IC turns on its own. But I'm not sure if that is the actual intent, or if it's just the "distract IC for X turns while it Attacks something un-attackable."