In the Matrix, this just is not so. If you fail a Hacking + Stealth roll versus the system's Firewall + Analyze, it immediately knows you're there. It sounds the alarm immediately. All security spiders in the system are immediately available to kick your ass, all active IC is immediately available to kick your ass. It would be as if the building's entire security forces beamed in from the Enterprise right in front of the gates and rolled for initiative the moment you get spotted trying to break in.
And, of course, if you're capable of overcoming that, the system still has a fallback that you can't beat: it can shut itself down, ejecting you and Dumpshocking you if you were in VR. This would be equivalent to the building radiating a mystical pulse of energy that ejects your whole team from the mission and scrubs the run right then and there because an impenetrable forcefield just went up.
And, of course, if you're capable of overcoming that, the system still has a fallback that you can't beat: it can shut itself down, ejecting you and Dumpshocking you if you were in VR. This would be equivalent to the building radiating a mystical pulse of energy that ejects your whole team from the mission and scrubs the run right then and there because an impenetrable forcefield just went up.
Well, that really depends upon the system's ARC. For example, Most of the tough systems we have cracked had an ARC that tried to boot the intruder first. Thjen it activated IC if it was unsuccessful (and only the IC in the node was immediately usable, any remote IC had to travel there, which takes time), and if that faiuled, then SPiders were notified and the weight of the system came down upon you. MOST such systems cannot just shutdown, as it causes havok with the onsite people.
The Zero Zone was a bit more difficult, as it had Active IC already in every node, and the ARC alerted Spiders first before trying to dump the User, all the while the IC was doing its thing against the intruders. Biggest issue with IC loading to the node is that it slows the node, which is counterproductive most of the time for the system, so there will likely be a limited amount of IC available for any given node. Once that limit has been reached, well...
There are things a GOOD Hacker can do to extricate himself from this situation. Our hacks run very similar to how Decking actually ran, except that it is 20 times faster, as it flows with the physical combat of the scene. Everyone stays in synch and we move as a team. *shrug*