1

I had a friend try to convince me today that simply by signing into a wifi network, without any physical access to your computer, the network admin can see your computer's screen.

Obviously this is false, but I don't enough about networking to explain why. Can someone explain what prevents a malicious network from having remote view of your screen?

  • 1
    do you also mean "without infecting your computer"? Just from network traffic, alone? – schroeder May 28 '15 at 23:35
  • Yes, as in my computer, with up-to-date antivirus, etc. The only thing I've done is logged into his network. – Jon May 29 '15 at 0:05
4

Your "screen" includes many elements that never get transmitted over the network, so there is no method by which anyone on the network could see those elements. For example, if I set my desktop wallpaper, no one on the network can see that.

Might it be possible to see a user's browser window (i.e. reconstruct a clone of the traffic to the computer)? Yes, under certain circumstances. By having access to the network, it is possible to capture the packets and then reconstruct them page by page or update by update. But, the traffic would have to be unencrypted (no SSL/TLS or VPN tunnels).

All this assumes that the malicious network has not also installed something on the computer.

2

Schroeder's comment to your question implies the answer: No.

To get to your specific question, a malicious network can see only your network traffic. You can install something like Wireshark to see what traffic you are sending. That's what a network operator can see.

But that's a conditional "no." There is software that will allow screen sharing, i.e. snooping, and if such software is running on your computer, whether because the computer belongs to the company and they've installed it, or because it was installed surreptitiously, then yes. Unless the software is pretty sophisticated, you'd be able to see the screen sharing traffic with Wireshark, and you could certainly see it with an external network monitor.

  • 1
    Question says "network admin" and no machine access so the screen sharing part of your answer isn't relevant. – Neil Smithline May 29 '15 at 1:29
  • @NeilSmithline: There are several ways to install software without physical access to the machine. I give you drive by downloads as one example, and software push to a computer logged in to an active directory domain for a less sinister and more certain example. – Bob Brown May 29 '15 at 1:32
  • Doesn't sound like there's Active Directory but if router is under control of attacker I guess many injections are possible. Good point – Neil Smithline May 29 '15 at 2:18
-1

as a network admin, I've done this before with VNC to check if users were watching porn. but note that VNC was setup in those machines by default as part of the image.

there are two things necessary to watch the screen in realtime:

  1. have network access to that PC.(wifi or wired or whatever)
  2. there must be a program like VNC or some malware installed on that target.
  • 1
    The OP's point is that nothing has been installed. He is a guest on the wifi network. – schroeder May 29 '15 at 19:32

protected by Community Apr 15 '16 at 22:58

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