Mirror Theory, it's hard to explain. Remember, it is only a theory, only a possibility. There is no right or wrong, just guessing and possibilities. The reason I call it a "mirror" is because of the fact it takes what we know, however, we do not see it. It involves the chat room.
How I think it works is the Ivichs are in a chat room replica of this one that reflects off of our own. Think of it like an underground chat room we can't access. From down there, they can see what we're doing from above, yet we have no clue what's going on beneath us. It's basically spying on chat without being in our chat, yet a copy of it. They're able to see our conversations, even private messages (maybe). They can log this if they find anything they may need to know and use it for future reference.
I've had incidents a year or two ago when the Timer started popping up of random people coming into my chat rooms. I remember one specifically over at the BDYT Wiki an incident. There were three users in chat and it all acted up again. One said "That was fun, let's do it again!", the other said "Guys, look...", and the last guy said "Refresh". I refreshed too and they all disappeared. I don't remember their usernames sadly.
It's very possible they're continuing to use this "mirroring" because they know there is nothing we can do about it at this time. If this is right, kudos to them on this smart planning. I think it would've gone better and unnoticed without the Wikia bugs from a while back.