The Matrix has evolved to a level where everywhere is an UV level (hyper-real). The way to get there is through hot sim, but every commlink can do it. The norm user doesn't even have computer skills anymore because you can use your every daily skills to go and work in the Matrix. It is like the real world.
Agent-Programs and IC are like common people, corp-zombies, they are limited AI, and react like people do. But that way has its perks you can act like in the real world, you can charm your way in, you can lie to a program, you can fight it with your bare VR-hands or use weapon-programs, you can sneak in or infiltrate a security node, like you would in the real world.
But you could be injured and even be killed as well, here in the Matrix.
What is a hacker?
A hacker can bend the rules of the Matrix to his advantage. Changing little things like hacking a lock of a VR-door, wouldn't be detected in most systems, but changing the laws of physics in the whole node, is a major change and will immediately detected by the system and if you haven't the right security clearance the system will hunt you down. Hacking is cheating the laws of nodes nature.
In terms of rules, there are manipulation or hacking levels, from small changes to major changes, each has its own hacking threshold, interval and detection threshold modifier for the system.
The System
The System is the nodes metaphor, its over-watching god that make sure that every detail of the created metaphor is in the right place. But like god it is not really there or walks around it is more like a background existence or laws of nature, it has its own intelligence but it isn't designed to interact with people. It runs the node, more like a written destiny or law of nature. If something is wrong with the system it has to be fixed by someone or something that can fix it. The System can't do anything by itself, only detect things and command fixes.
Programs
Programs comes in many forms and shapes, everything in the Matrix is based on programs.
Most of the things you can see and experience in the Matrix are one purpose programs, designed to fulfill one thing. For example landscape programs are there to create an illusion of a place. Rocks, sand, a beach or even the sky has no other purpose like giving the illusion of its real counterpart (if it exists in real life). A "one purpose" rock program could not used as a weapon. Most systems are designed to protect its legitimate user form harm.
Equipment programs are things that can do things or can help doing things. They are mostly the equivalent of equipment in real life. i.e. a VR-Katana program is like a Katana weapon in real life to use with the real life skill to handle. A VR-lock-pick set does the same as a real one would do. And the best of it, it costs in most cases the same as its real one, and has the same Availability.
Social programs are the people or animals in the Matrix, they are programs with a personality program integrated, it reaches from VR-animals that act exactly like real ones would but with extra options, like always friendly or doesn't need to eat or pee. Through VR-People with a limited AI and Persona-Fix programs. In most cases VR-People are complex programs that has to interact with real people users. For example most commercial IC programs are designed as Security Guards or Police Man. The price for the program decides about its intelligence or range of possible actions or actions off the core programming. There are a couple of programs with real Independence, so called AI, this programs are a new kind of intelligent beings were born in the Matrix and live here as every other program, except they knew about themselves being programs and the Matrix, these self-awareness is rare, most of the limited programs do not reach that level ever. But a self-aware AI can do things another program can't do, like hacking, or programming. There core programming is no longer a limitation for such an AI program, it is an extra set of integrated options that it has at hand, if it needs it.
Game Terms or Rules
The Matrix works exactly like the physical world of SR do. Exceptions are defined by the Systems Metaphor. All actions will be done with the usual skill + attribute test.
The only thing that doesn't work in the Matrix is direct Magic. Because Magic needs a mana connection and does not go smooth with technology.
But the magicians of the Matrix are called technomancers and they follow the mostly same rules as magicians do, with a couple of slide changes.
What does that mean?
It means everyone can jump into the Matrix and act like it would be the real world. And everyone relies on his or her real skills. A good fighter in the real world is a good fighter in the Matrix, a con-artist who can talk his way into a secured area, can talk his way through the Security IC as well, aso.
Hackers and Technomancers or full aware AI can hack the world, they can do Magic if you like to call it that. Hacking is an extra set of Abilities a character can have to change the virtual reality around him. They're roughly like spells, adept powers, metamagic or creating equipment that do magic tricks, etc.
[to that point I haven't an exact rule set for hacking, but it should be as nearly as possible to existing rules.]
For example technomancers jump into the Matrix like magicians project into astral space and use their mental Attributes as base for their Persona.
Hacker Programs could be like magical focus or spirits.
And Hacking Abilities are like adept powers, such as improved ability or improved reflexes or wall-running traceless walk...
The Hacking Skills are maybe similar to magical skills, i.e. Counterspelling would be Anti-Hacking-Protection (don't bother the name isn't fix) or Hacking is similar to Spellcasting.
I said it, it is not really ready but the base of my idea is there. Break the Matrix rules apart or melting it into existing, easy understandable or even intuitive rules.
Yours faithfully,
UV