The BK example is actually riddled with mistakes so it is not a very good example to use to be honest, but it works for the question you have in this topic. Ill go through it step by step.
If you want to look at what's behind someones's PAN you gotta do some hacking.
Unlike other editions, devices in 5th edition are accessed directly. There is no Router or Server or Master Device you have to first hack in order to then hack devices that are part of a PAN. They all show up as icons of their own. And you spot them individually. And you hack them individually. Being part of a PAN or not change nothing (except that it might get to defend with a higher firewall rating).
Any filtering is done on the observer side. You (or rather your commlink) filter stuff for you all the time. If you choose to not filter anything (you can choose that if you like) then you would be blinded by all data streams. You would see nothing.
SR5 p. 218 The Population of the Matrix
Every icon in the Matrix is one of six things: a persona, a device, a PAN, a file, a host, or a mark. Occasionally, you might also see a datastream, a transfer of data that looks like a thin beam of flickering, multi-colored light. Datastreams are normally filtered out of your Matrix view because if they weren’t, they’d be the only thing you would see. If you want, you can dial back on the filtering, but the streams pass by so quickly that you can’t tell where they’re coming from or going to without snooping on whatever is sending or receiving them, and that would be illegal (and we’d never do anything illegal in the Matrix, right?).This is mentioned in several places in the book. Here is another example:
SR5 p. 217 Virtual Visions
The first piece of assistance comes from your commlink, which automatically filters out the least interesting icons. Do you want to know the virtual location of every music player in the world? Right, neither do I. So the Matrix will usually show you an icon for an individual’s personal area network (PAN), not every device in that network (although it makes exceptions for interesting or dangerous devices in that network, such as a gun). Additionally, the farther away devices are from you in the real world, the dimmer their icons are in the Matrix; this is partly because your commlink figures the farther ones aren’t as interesting to you, but mostly because the connection is a bit slower due to the distance. Matrix gear renders the far-off devices and personas as dim, muted, or flickering icons. Also cutting down on the visual noise is the fact that some icons are deliberately hidden from view, such as locks and other security devices, baby monitors, maintenance monitors, and of course people who prefer not to be seen.The example you are talking to is also mentioning that it is the observer that filter out what icons he want to see. Not the target PAN.
SR5 p. 224 Example
He’s in AR mode, with device icons superimposed on his vision. Right now he’s filtered out most of the icons...I was thinking of that example too, but in that case I take the waitress' carelessness to mean she hasn't slaved it all to he comm and protected it sufficiently
Files cannot be slaved to your commlink (only devices can be slaves).
SR5 p. 235 PANs and WANs
Only devices can be slaves, masters, or part of a PAN.it's not just out there for everyone to see.
Actually, files that are not protected can be read, viewed and listen to (this does not require a mark).
If a waitress have music albums that are not protected then anyone can listen to them.
SR5 p. 222 Life With a Commlink
Most of what you keep on your commlink are files, this includes music, your SIN (fake or otherwise), licenses (also fake or otherwise), maps, email messages, your contact book, AROs, and so on. These files are visible to people who can see your commlink in the Matrix, so most people keep all of their files in a protected folder.The example you are talking about also mentioned this:
SR5 p. 224 Example
but since the waitress hasn’t protected her commlink’s privacy, he’s flipping through her music collection in a little virtual window that is linked by a pointer to a pouch at her hip.But even if the file is not protected you still need to place your mark if you wish to change, copy or delete a file icon.
SR5 p. 239 Edit File
Marks Required: 1
Edit File allows you to create, change, copy, delete, or protect any kind of file.And there are only three different ways you can get your mark on an icon. The owner invite you to legally place your mark on his or her icon. You illegally force the icon to accept your mark (brute force) or you illegally trick the icon to accept your mark (hack on the fly).
SR5 p. 236 Recognition Keys
There are three ways to get a mark on an icon. The first is the legitimate way: the icon invites you to add a mark....The other two ways are by hacking, both Matrix actions: Brute Force (the loud way) or Hack on the Fly (the sneaky way).This is also supported by the example (where he first listen to the albums he like - since the file is not protected he does not have to take the illegal crack file action and can simply listen to the albums before deciding on what to copy, then use the illegal hack on the fly to gain the access level he need to actually copy the album)
SR5 p. 224 Example
Seeing an album he likes (and having little respect for the law), he sleazes a mark...While Edit File to copy the album is a legal action, Hack on the Fly to place the mark needed is not... this it is causing ripples in the matrix that GOD is reacting to... within an hour or so GOD will converge on BK unless he reboot his deck.
The example talk about this as well:
SR5 p. 224 Example
The mark flashes a little as it helps him copy the music file from her commlink. He knows this bit of mischief could be discovered by the Grid Overwatch Division, but he doesn’t care. He’s already enjoying the first cut of the album.