Help on Apache Attacks

Hi, I was wondering if someone can help me protect my server from Apache Attacks, they are extreamly lethal and I have seen one hit me before and it just shuts the entire server down, can someone help me out with making sure if someone does try to attack then my server can go back and say NO NO NO, and block there ip?

What sort of attacks? Just a DDoS? You could try investing in some sort of IDS which analyses http attacks, or if you find it's always coming from a certain block of IPs, just add that block to your deny in .htaccess or something