Best way to kill the Internet?
 

What is the most recommendable way to switch off the Internet connection temporarily? (probably by using some terminal commands)

Ideally, it would be good if the connection could not be restored in seconds but it would take at least half a minute or more to get it back.

(I have got a picture that according to the research literature on work efficiency, it helps a lot if disturbing factors are at least at the distance of 20 seconds)

How these software solutions compare to pulling cord off from an ADSL modem?

Best way to kill the Internet is not to sit before the computer.

Depending on your distro, use ifup <your interface> & ifdown <your interface> as root or sudo.

If you want to keep the LAN connectivity alive then removing the default route with
and restoring with 'ip route add default via <gateway router address>' eg

pull the plug?

http://www.biggercheese.com/comics/0332.png

Mentioned in the first post.

arptables -P INPUT DROP

Assuming you're in an IPv4 environment...

What in the world does that mean?The right software solution is exactly the same result as pulling a cable.

It would be helpful if you explained better what your intentions are here. I thought that maybe you wished to disable it to avoid someone like your child from getting on the Internet when they weren't allowed. Talking about work efficiency is the opposite of what I'd think because if the Internet was not available, a large amount of myself and peers would be limited in our work capabilities. If you're talking about removing distractions away from employees so that they can do work as opposed to surfing the network, that's a management problem not a technology problem. They'll find ways to not work and likely many of them have other means to get to the network besides their desktop systems.

And if this is all philosophical, I'd instead recommend the Non-Nix->General forum instead.