If your Administrator don't secure,
If your ISP don't change default config,
We can HACK your Local Area Network !
Your LAN will "Stop" anytime we want
Here's HOW ...
Connect to your Switch Manager: Type the Switch's IP on Address bar and change some configurations.
An Easy Example:
> Click to "Port Configuration" or "Port settings"
> Select one (if you want 2 select more, Press CTRL when select or select multi ports)
> Click to Disable (or uncheck "Enable")
> May be you have 2 Click to Submit
OK ! The PC connect 2 that Port can't connect to LAN, Internet.
If you try to plug, unplug, that PC still can't connect.
(You can search a lot Tools on Internet that can Scan all IP Adresses on LAN, it make you can know what're IP addresses of Switches, Routers ... )