Thanks - I was thinking of Hack on the Fly(I misphrased it i guess), I get that any resisted hits from the comlink would give him net him + to overwatch score, I was more curious about the NPC knowing that he was being hacked. My thought process being adding the intuition would imply the user's brain power is involved, thus making him aware. And was also thinking of the way normal combat is done, a surprise attack that someone doesn't see coming, doesn't get defense so I guess I sort of expected a similar rule in the matrix. I re-read the matrix section and I found my answer, pg 237 under [Matrix Actions] - "When a defense test calls for a Mental attribute, use the owner's rating. Even if she isn't currently defending or even interacting with the device, her previous interactions and settings affect the defense test."
Ok I just want to make sure I've got it right(or at least been running it right thus far). If for example you do Hack on the Fly, its Hacking + Logic [Sleaze] vs Intuition + Firewall ; As long as the hacker gets more net hits than the thing/person getting hacked they place a mark without said thing/person being aware ? (and of course the OS goes up for every hit from defender)