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My school supposedly cuts everyone's connection at exactly 12:00am. Although the network is still there, Windows shows the "no internet" sign when connecting to the network.

However, the strange thing I have been noticing is that although the school wifi blocks new connections (for example connecting to a new website or watching a new video on youtube), it doesn't seem to care about the connections that it already has (for example, it doesn't cut your connection when you are watching an hour-long youtube video).

Also, it doesn't seem to block your connection if you are continuously connected to a VPN, but cuts you off as soon as you disconnect from that vpn, even when you turn your VPN back on.

Does anybody have any idea how this internet connection control works? (if it is used widely and has a name, please tell me) And is there a way to bypass this block without connecting to a VPN?

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    Why on earth is this control in place ????
    – schroeder
    Nov 19, 2020 at 11:08
  • because the network admin doesn't want students to be happy :(
    – Andy_ye
    Nov 19, 2020 at 11:15
  • Here is an important lesson for infosec: if you try to control something that cannot be naturally controlled, people will find a way around it simply because they can...
    – schroeder
    Nov 19, 2020 at 11:16
  • @schroeder make doing it the secure way the easy way or all your users will become hackers. Nov 21, 2020 at 17:25

2 Answers 2

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It looks like they add a rule to the firewall to deny outgoing connections. Since it is a stateful firewall, any new traffic is a new "connection". Existing traffic streams are unaffected since it is not a new "connection", but a part of the existing stream.

VPNs are a constant connection and traffic is tunnelled through that.

Example using iptables:

iptables -I OUTPUT -p tcp --dport ANY -m state --state NEW -j REJECT
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  • Is it possible to force my computer to keep a connection that I want open so that I will be able to connect after 12am? or is there any way to keep a vpn-like connection locally?
    – Andy_ye
    Nov 19, 2020 at 11:14
  • Use a VPN? You can make your own using cloud resources
    – schroeder
    Nov 19, 2020 at 11:15
  • I was hoping for another solution than a vpn, but if using a vpn is the only way, then thanks!
    – Andy_ye
    Nov 19, 2020 at 11:19
  • There are proxies and other options. I'm not sure exactly how the block is written so I can't point to something that would work. You could experiment with different options, like Tor.
    – schroeder
    Nov 19, 2020 at 11:31
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With such a control in place, there's probably some reasoning behind it and, therefore, any attempts to bypass it may result in more strict controls. They could close already established connections, detect and block VPNs or even turn the switch ports or WiFi SSIDs off for the night.

The only real solution is to get an internet subscription that is independent from your school. Or accept the situation, sleep longer nights and be more prepared for the next day at school.

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    As someone who uses YouTube to get to sleep I find no reason to think this would make people sleep longer. This would literally keep me up at night. Nov 20, 2020 at 17:30
  • I'm not saying it's a good reasoning - just that they have one. Nov 20, 2020 at 18:20

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