Disallowing ICMP echo requests on DI-524 router

I've recently been a victim of several denial of service attacks, the perpetraitor flooded my router with ping requests. I've looked the problem up on Google and found that I need to disallow ICMP echo requests on my internal network. So I went to my routers control-panel-type-thing and noticed that it was set to "Allow" by default, correct me if I'm wrong. So my question is how do I disallow or deny it? The first "rule" in firewall rule list doesn't seem to be editable. Here's a screenshot

Edit: Nevermind, sorted. A nice gentleman replied to me on Yahoo Answers. http://support.dlink.com/emulators/di524/tools_misc.html Thanks anyway.

http://support.dlink.com/emulators/DI524/tools_misc.html

it's under tools