These are extra rules introduced in supplementary material such as Rainworld: Cyberdeck and Rainworld: Altitude.
You don't have to use them, but they are intended to round out areas of the rules which might come up in play, where the corebook is light on detail or has no suggestions at all on how to deal with the situation.
In the core rules, using a computer for anything, including hacking, is just a question of using an object (the computer) or Software skills rolls.
Rainworld: Cyberdeck introduces the idea of using a cyberdeck, or decking. (In Rainworld terms, a "cyberdeck" is just another computer — usually a high-spec one with a lot of expansion ports, but not a special type of hardware in itself. Decking can be done with any computer.)
Characters with different initiative conditions can act up to 3 times per round. Computers, too, vary in speed, and can perform 1-3 decking Basic Activities per round. (If a computer doesn't specify — such as the corebook personal computer — it's a 1-action device.)
Decking posits every computerised system (which, on Rainworld, is practically everything) as a hierarchy of nodes. Every node represents some piece of hardware, software, or source of data.
Nodes can check the identity and credentials of anyone trying to connect to them, in various ways. (The possible policies include "don't actually check".)
The decking Basic Activity can be used to:
Not all nodes support all verbs; a temperature sensor probably only supports Read, for example.
When you direct a drone to shoot at people, you are not doing the shooting yourself; it does not use your Firearms skill.
Rainworld: Altitude introduces the Handling stat for drones. When being directly commanded by a person, to perform a task it was specifically designed for (such as shooting at people, for an armed drone) the drone's Handling functions as a skill bonus to the roll (i.e. 2d10 + Handling). Drones which do not list a Handling rating have Handling 0.
Drones take the same penalties as people for taking unaimed shots; however, unlike people, they don't need to do separate Activities to draw or reload their weapons.
Sensor data is ubiquitous on Rainworld. If you can't see, but you can feed, say, a squadmate's OmniHUD data or the building's CCTV into your PineaLink, it's possible to use that to undertake tasks, such as shooting at people you can't directly see.
Any tech which usually makes aiming an Adjunct Activity does not apply when perceiving via indirect sensory input. Indirect-sensory aiming requires a full Basic Activity.
Relying purely on indirect sensory data incurs a −5 penalty on your roll. However, you simultaneously receive a bonus to the roll equal to your ranks in the Coordination Quirk (even if you negate the penalty by taking the POV Plasticity Quirk!)