what plugin for spam comment

recently I have a trouble with spam comment on my blog http://mhsang.com/coupons/get-20-off-with-web-hosting-coupon-at-hostgator/
And I see some blog install the function like
{
Tick to confirm that is not spam
Tick to notice about replies via email

}
Anyone’s using this plugin, please tell me the name of that plugin.

Thanks sao much.