Honestly you cannot stop an organised team of griefers. AVO, ICanHasGrief, AusMinecraftGriefers, etc. They are good at what thye do and they do it for giggles or a purpose. So these guys will have hacked or altered clients that have some nice perks. Aimbot, x-ray, fast-running, insta-kill, nuker; anything that'll speed up the process.
SO here's what you do. If you own a server, you get some very good protection. Something that blocks custom clients, block protection, proper backups, chest & furnace protection, things like that. Cover all the bases so that in an instance where a griefer team join, your server will server minor damage. Also don't just hand out Creative mode to people so fast - trust is key. You can't get around them all though.
For the odd griefer, traps and cleverly hidden chests can protect the important things. My personal favourtie is to put a chest down at bedrock layer and cover it up. Try finding that