Well, I think it highly depends on what sort of creature we're dealing with. If it is a ghost that's gotten into internet, the agenda could be virtually anything. But I feel like it would be cooler to have something new, creating a new mantel, if you will.
Now going with that, I'd say there are 2 types that could be out there. One would be an AI that was either created with a purpose in mind or emerged out of something. In any case, this would definitely have an agenda, and it could be relatively free as well, depending on what it was designed to do or what happened to make it emerge. Could be neutral, could be good, could be evil.
And then it could be a virus. A virus would simply want to spread itself around and damage, deceive, corrupt, etc. Bad stuff.
Now I think an AI would be more interesting for a player character. It could be spliced off Wikipedia, being sort of the AI version of Ivy, gathering knowledge wherever it can. This would be rather neutral, I'd say, knowledge can be used for good and for evil, but it isn't any of those inherently. Other AIs are possible as well, of course. A top of the line security system going rogue. This one would probably view the place it was set up to protect as its home, but it would be able to work anywhere there is wifi. Or a spy algorithm gone rogue, gathering and analyzing data about people. And so on.
Now depending on what's what, it would probably change the kinds of "spells" you can work. A lot of it would probably be divination though, the internet is THE information highway, after all. Though it seems to me that none of them would want to overload a device to kill it, because that would mean one more device they can't use their power on. Instead, I would say it makes a lot more sense for them to be able to highjack those devices instead and make them do stuff they can actually do. A phone going of can be enough of a distraction, after all, to sneak in somewhere, so why maim someone with it? And you can use it for so many more things once you've got a link to it.
You might be interested in reading up on some Shadowrun. I've not looked into 5th edition yet, as I don't have a group to play it with. But this has existed since 4th edition, so that should be fine. There are, among other things, technomancers. Basically people who are born with the ability to interface with the wireless internet (called the matrix) without the need for any technology, like regular folk use. There are also some AIs, one of which is famous and has taken over the entire matrix for a while. There are also things called sprites, that are basically the technomancers versions of ghosts. Short, little programs he can summon up to do his bidding. There's an entire book on the matrix and how it works for the game, I'm sure you could draw lots of inspiration from there.