They can't.
An IP address consists of a string of four numbers ranging from 1 to 255, this is known as IPv4 and is, I believe, still the standard (although there's a new standard out there that's more complicated).

My knowledge of IP is incomplete, so I'll explain this as best I can.

If you imagine a housing estate, each house represents a computer and in order to post a letter to your house, you need to know the precise address. The first number refers to your home city, the next to your housing estate, the next to which street you're on and the last to the actual house you live in. All well and good. If you wanted to stop the members of house 164 from receiving letters you'd just have to block the house number.

That would be nice and neat, but it very rarely works that way anymore. IPs are usually dynamic and you'll be given a new one each time you connect. Instead of a row of 255 houses, you've got 255 post boxes on your street, any of which can be assigned to you at any given time. Suddenly the only way to be certain of stopping you from getting letters would be to stop letters going to your entire street. Obviously the other residents won't be terribly happy about that.

That's far from the only problem, you can go to sites that mask your IP address, for one.

Broadly speaking, the street address will be roughly analagous to a company, or an IP provider. So you can see that simply stopping service to a group of IP addresses in order to stop one person is something of a last resort. I can only imagine what this Bou person did to get an entire country's IP range banned. As escalations of hostilities go, that's a whole order of magnitude. Truly biblical beakering.
( Kroney, Sun 8 Aug 2010, 17:15, 4 replies, latest was 16 years ago)

"Truly biblical beakering."
excellent phrase that.
( blaireau69 , the Cumbrian Travis Bickle., Sun 8 Aug 2010, 18:54, Reply)

Anyways yeah, so I didn't say they'd banned his IP
I just said they were onto it.
You got any rice?
( Roota zweeeeeoooooowm, Sun 8 Aug 2010, 19:04, Reply)

aye you didn't
I am just starting vicious rumours AGAIN
( rachelswipe with a fork, Sun 8 Aug 2010, 19:07, Reply)

LIBEL!

( Roota zweeeeeoooooowm, Sun 8 Aug 2010, 19:28, Reply)

rice ris?

( Kroney, Sun 8 Aug 2010, 19:15, Reply)

I just fancy some rice.

( Roota zweeeeeoooooowm, Sun 8 Aug 2010, 19:28, Reply)

Does brown bother you?
I may have some ancient basmati in a cupbard somewhere.
( Kroney, Sun 8 Aug 2010, 19:30, Reply)

Im not one for rice so I cant help sorry
apart from these ASCII rice grains; ...................
( willenium Fist bump for verification, Sun 8 Aug 2010, 19:33, Reply)

Ta folks
I need it cooking as well
( Roota zweeeeeoooooowm, Sun 8 Aug 2010, 19:46, Reply)

I've got lots of that "2 minute in the microwave" sachet rice
But I am all about the mushroom compote these days.
( The Light in Chains don't touch the Pope's boner, Sun 8 Aug 2010, 20:51, Reply)

Thanks for explaining
I was having trouble understanding why we had to lock out all of SA
( willenium Fist bump for verification, Sun 8 Aug 2010, 19:28, Reply)

So er what I said then yeah?

( fuck shit up the best you never had, Sun 8 Aug 2010, 23:00, Reply)

I thought
rachelswipe might want to know why it couldn't be done. Just trying to be helpful.
( Kroney, Mon 9 Aug 2010, 8:36, Reply)