Well this is not has simple as that, we have quite a good Admin, really good, but it seems that even with our firewall we are still victim to some nasty attack.

I really don’t think it is competitors or angry vendors that are causing the mischief. It’s probably just some kids that got some beef with ya for a reason nobody knows probably. You’ll have to wait 3 or 4 years til those kiddies can get a job.

DoS comes in many forms, and whilst a firewall can prevent (say) a SYN flood and/or block networks completely, a simple DoS which saturates your internet connection cannot be stopped without either buying lots more bandwidth or getting your upstream to filter IPs or rate-limit. Not many ISPs are able to do this effectively.

Another technique is to have multiple circuits, multi-home your public servers and use DNS to spread the load. However, a coordinated DoS will kill that too. So you need mirrored sites too. And this all gets expensive.

The best way is to find the people committing the DoS and LART them.

DoS sucks
i got that once too from Korean IP address
suddenly there were lots of Korean IP addresses accessing my site..
and it became slow