Block and unblock access to certain domains

Question

How can I block complete access of my computer to certain domains but be able to switch it on whenever I want to? That is, I want that by default whenever my browser or any other application hits a page of the form http://something.domain.com, or a page who is somehow connecting me to http://something.domain.com — that it blocks it and don't send anything without my explicit consent.

I know we can block something completely by using hosts, but the trouble is that I may need to check these domains once in a while, so I would have to keep removing and adding it to hosts. Which is ok if I can refresh it somehow, or have a script do it quickly for me.

Is there a simple way to do it?

I have the impression it can be done with iptables, but this is a subject I am not familiar with.

Answer 1

There is a Linux version of SelfControl program which essentially does that - blocks a list of domains for a specified number of hours. It does this using iptables, so you may consider it a nice wrapper for shell commands. The difference from your description is that it intentionally makes it difficult to unblock a domain - to make self-control a bit easier :)

Other options, such as editing /etc/hosts or writing a script which adds/removes an iptables rule - are also viable.

At least you can study SelfControl source to see how it manipulates iptables.