Wi Fi Issues

For the last two days the internet has been very slow. Lots of web pages timing out, emails taking a life time to load.

What is the problem.
1. A virus?
2. Our machines have been recruited on a DDOS attack?
3. Firewalls?
4. Windows messing around.

A month ago I had big trouble installing a new adsl router. So the first thing I do is stop all firewalls on the network. What I forgot about was the Wi Fi side of the router which as default is left open so anyone with a laptop or pocket computer within 100 yds of the house has free access to the internet through our WiFi. Whilst not completely against the occasional sharing I am not up for someone else using our full bandwidth to down load a film etc whilst we struggle to load a web page.

So now the WiFi security is 128 bit enabled. No more free internet to my little friends with laptops.

key suspects clue: China